Sixteen months ago, Altiero Spinelli, 70, a respected former member of the nine-man commission of the European Economic Community, was elected to Italy's Parliament on the Communist ticket.

Retired Air Force Gen. Nino Pasti, 68, who once represented Italy on the NATO military committee, also won election to Parliament as a Communist candidate.

Neither man is a Communist.

"It's all rather ironic," chuckles Spinelli, who along with pasti and a number of other independents was offered a slot on the Communist slate in the June 1976 election - and promised freedom from party discipline if he won. Thirty-eight of these non-Communists were elected to Parliament.

"It was a risk for them, and a risk for us," says Spinelli. "But so far, it seems to be paying off."

A growing number of Italians, in fact, are coming to view the Communist Party's open-arms policy as a shrewd, long-term political calculation.

Admittedly, the Communist leadership is occasionally embarrassed when the independents break with the party in Parliament.

But on the plus side, Italian Communists point to the independents as proof of the party's commitment to pluralism.

Analysts speculate that the Communist Party is also looking to the day when one or more of these non-Communist Communists might be included in a Cabinet.

Such a step would enable the Communists to take another giant step toward power sharing in Italy, while continuing to stop short of formal participation in a Christian Democratic-led government.

Whatever the Party's motives, most of the 38 independents elected to Parliament with Communist votes seem convinced of the Party's good will and satisfied with the freedom granted them.

Because the independents are not party members, they cannot attend party meetings and, with some exceptions, find it hard to influence the making of policy.

But discussions with several of the group's most prestigious members indicated no complaints of Communist pressure - even where views conflicting with policy have been expressed.

Piero Pratasi, 52 a Catholic jcurnalist who once edited the ruling Christian Democrats' party newspaper, says he decided to run on the Communist ticket to promote "greater understanding between the Catholic and Communist worlds."

Pratsei one of six Catholic deputies who opted following their election to join the Communists' official Parliament group, has used his freedom from party discipline to challenge the official Communist's stands on abortion and a new military plane. However, he does not think the significance of this autonomy should be exaggerated.

"We are too few and too much in basic agreement with the party for it to be said that our independence has yet undergone a major test," he says.

Altiero Spinelli, on the other hand, thinks it significant that the party has provided the freedom it promised. Spinelli, like the majority of the independents, declined to participate in the official party group and is a chariman of a separate "mixed group."

"For the most of us, this may reduce the chance of influencing policy at its origins but it Spinelli guarantees us total freedom," he says, Spinelli notes that in August 1976, he voted against the formation of the present government of Guilio Andreotti, while the rank-and-file Communists tactically backed it abstaining.

Geno pasti, who retired from the Air Force in 1969, describes the Communist Party as "basically pragmatic" and says "I am competely free to vote according to my conscience."

In meetings of the defense commission he disagreed openly with party policy on Italy's MRCA air-plane, and ultimately voted with the party on the issue "only because sometimes the political aspects of decisions outweight the technical considerations."

Spinelli, who feels he probably has "more influence" than most of his independent colleagues because of his expertise is European affairs, says it is hardest to influence Communist Party policies when they have already crystallized.

Nevertheless two economists in the group have criticized the party openly and in print.

Claudio Napoleoni, a Turin University economics professor, has written scathing articles chastising the Communists for their subservience to the unions on economic matters.

Luigi Spavanta, 43, an economics professor at Rome University who describes himself as a Keynsian rather than a Marxist, says that in recent months he has openly differed from the Communists on university reform, public order, industrial reconversion and a controversial dividends witholding tax.

Despite, this says Spaventa, his relations with the Communists remain excellent, and he is striving to help the Communist Party on economic policy wherever possible, and to sponsor useful laws in Parliament.

"We independents can also keep an eye on Italy's two major parties, reminding them that if they do go ahead with the historic compromise, it must be to better govern the country rather than to divide it up between them," says Spaventa.

Sen. Renato La Valle, the former editor of the Catholic daily Aveunire and author of three volumes on the second Vatican Council, feels he was able to influence the Communists on at least two sensitive issues - abortion and the neutron bomb. Nevertheless, he sees his role as a temporary one.

"My goal was to help to pull out the plug in the dike separating the Catholics and Italy's Marxists, after which history will take its course," he says. La Valle points to the growing cooperation between Christian Democrats and Communists as an indication that he and his fellow Catholics have already made considerable progress.