With Connecticut in the lead, eight Atlantic Coast states ranked among the 10 in average incomes, the government reported Thursday.

The Commerce Department said residents of Connecticut earned $21,266 for every adult and child in 1987, an increase of 8.8 percent over 1986.For the nation as a whole, incomes rose 6 percent to an average of $15,481 last year.

Mississippi ranked last with a per capita income of $10,292, a 5.2 percent increase over the previous year.

Eight Atlantic Coast states plus California and Alaska made the top 10 income list while seven of the 10 states with the lowest incomes were in the Southeast, traditionally the region with the lowest incomes.

The revised figures showed that income growth in the United States was stronger than originally reported four months ago, with some states moving up slightly in the overall rankings although the top and bottom spots were unchanged.

The original report put national per capita incomes at $15,340, a 4.8 percent rise from the previous year. The changes reflected data showing income levels higher than previously believed.

New Jersey, with an average income of $20,352, ranked second, followed by Massachusetts, with an average of $19,142; Alaska, $18,230, and Maryland, $18,124. Rounding out the top 10 were New York, California, New Hampshire, Delaware and Virginia.

In addition to Missisisippi, states with the lowest incomes were West Virignia, with an average of $11,020, followed by Utah, with an average of $11,366, Louisiana, Arkansas, Idaho, New Mexico, Alabama, South Carolina and Kentucky.

The report showed that regional income differences have been widening during the 1980s, something that usually does not occur during economic expansions. While states on both coasts have been doing well, heartland states dependent on farming, energy production and smokestack industries have lagged behind.