Maryland Gov. elect Harry R. Hughes continued the business of forming his cabinet today, appointing two new department heads and announcing that he would retain J. Max Millstone in his post as director of General Services.

Wayne A. Cawley, a farmer and old friend of Hughes who grew up on the Eastern Shore, was named to head the Agriculture Department.For the post of secretary of Human Resources Hughes picked Kalman Hettleman, director of the Baltimore City Social Services Department.

Today's appointments leave Hughes with half of his 12 cabinet posts filled and his administration beginning to take a definable form, following the firing of several department heads left over from the administrations of Gov. Marvin Mandel and Acting Gov. Blair Lee III.

Thus far, Hughes has surrounded himself with a blend of government technicians and independent progressives, with the cabinet posts divided between newcomers to state government and bureaucrats who served under Hughes' predecessors.

But while Hughes methodically went on putting his administration together, he found it difficult to get any attention for the people he had chosen to help him run the state for the next four years.

Instead, most of the questions asked at Hughes' press conference today and most of the gossip in the halls of the state office building dwelt on who would be running the state for the next four days, now that the Mandel's political corruption conviction has been overturned.

Time and again Hughes tried, with mixed success, to slough off questions about the impact of the Mandel decision and return to the subject of his cabinet.

Hettleman, Hughes said, "is really just moving up" from his post in Baltimore which he had held since 1976.

Hettleman, 43, who Hughes praised as "an excellent administrator," developed during his tenure in Baltimore a reputation as a social activist and an outspoken advocate of the poor. He had earlier served as director of the Baltimore Legal Aid Bureau, which offered legal services to indigent defendants.

In 1976, Hettleman managed the successful Democratic primary campaign of Maryland Sen. Paul Sarbanes.

Cawley, 55, has known Hughes "since both of us were old enough to talk," the new agriculture secretary designate said yesterday. "I lived across the street from him and his mother taught both of us in school."

Cawley was active in the Hughes campaign but said he applied for the job before talking to Hughes about his interest "to make sure I was selected on my record" as a farmer-banker, instead of friendship alone.

The reappointment of Millstone was accompanied by orders to make the General Services Department "more efficient, objective and sensitive," Hughes said.

Millstone, who last week joked that he was so anxious about his future that he would sleep on the office floor if it would help him keep his job, said he interpreted his selection "as a compliment because when it came to the 12 secretaries, Gov. Hughes conducted a very exhausting investigation of background and performance."

Millstone said it is clear that Hughes' priorities for his department include modifying procedures for selecting architects and engineers on state contracts and carrying out legislative directives for increasing minority participation on state construction jobs.

He acknowledged that "the potential could exist here" for abuses such as those disclosed within the federal GSA, but said that the likelihood is reduced because of the smaller size of the state department and restrictions enacted in response to allegations of abuse in the Mandel years.

"But it's not a perfect system," said Millstone who said Hughes wants the selection process to be "totally open."

Hughes resigned as transportation secretary in the Mandel administration over what he believed were abuses in the selection of architects and engineers, and his decision to run for governor.

Millstone, 50, has been a state ememploye since 1960. He moved up to secretary of the department in July 1977 after serving as deputy and assistant secretary in the Mandel-Lee administrations.