Two years ago Congress promised that the tax on a pack of cigarettes would drop by 8 cents on Oct. 1 of this year.

Now that promise is going up in smoke, and taxes in many areas actually may rise.

Chances are strong that Congress, under pressure to reduce the deficit, will renege on its pledge to reduce the federal cigarette tax.

In the meantime, state legislatures across the country are moving swiftly to fill the "tax gap" by adding their own 8-cent tax to a cigarette pack. And at least eight states are considering legislation to raise their tax even if the federal levy is not cut, meaning that the promised cut could turn out to be a tax rise instead for smokers in those states.

As a result, the cigarette tax has become the focus of a major national lobbying campaign this year, with tobacco interests fighting to block any increase and a coalition of health groups working to raise the tax as much as possible.

According to the Tobacco Institute, a Washington-based industry trade group, state and federal taxes today increase the retail price of a pack of cigarettes by about one-third.

At the end of 1983, the group says, the average price for cigarettes was 94.7 cents per pack. Of that, 16 cents was the federal excise tax and 14.5 cents went to state taxes.

The federal tax was raised from 8 cents to the current 16 cents in 1982. Congress called it a temporary increase. The legislation said the tax was to be cut in half, to 8 cents, at the beginning of fiscal 1986, next Oct. 1.

When state legislatures convened this year, they looked on the impending federal tax cut as an almost invisible way to raise state taxes. If the state tax were raised by 8 cents on Oct. 1, smokers would notice no difference in retail price, and the states would get increased tax revenues.

The Tobacco Institute says 19 states -- including Maryland, but not the District of Columbia or Virginia -- have cigarette tax increases pending. Most bills make the increase contingent on the promised cut in the federal tax, but the legislation in eight states would raise the tax even if the federal levy remains at 16 cents.

The Coalition on Smoking and Health, composed of such groups as the American Cancer Society and the Asthma and Allergy Foundation, has been lobbying for just that result. Matt Myers, a spokesman for the coalition, says a further increase in the tax likely would reduce smoking and benefit public health.

Steven Gold, of the National Conference of State Legislatures' Denver office, says it is likely that more states will jump on the cigarette tax if the federal rate actually is cut in half. "It's early yet," he said. "There's still a lot of time for a state to pass a higher tax and put it into effect early next year."

But if state legislatures are looking longingly at the tobacco tax, so is Congress. The scheduled reduction in the federal tax would cost the Treasury about $2.6 billion next year, exacerbating an already critical budget shortfall.

Sen. Bob Packwood (R-Ore.), chairman of the Senate Finance Committee, said he expects the federal levy to remain at 16 cents per pack. "It won't be raised, it won't be lowered, but it will be extended," he predicted last month.

To pass such an extension, however, Packwood will have to get around Sen. Jesse Helms (R-N.C.), the leading congressional bulwark of the tobacco industry. Helms says he will fight to the end against any effort to maintain the higher levy.