Semiempirical quantum chemical calculations were performed using the PM3 method to study the conformational equilibria of a series of 2-substituted carbonyl compounds in solution-a continuation of our previous work with the inclusion of an improved cavity model. The compounds studied were a series of substituted acetaldehydes CH(2)R-CHO and cyclohexanones C(6)H(9)OR(R=-CH3, -OH, -OCH3). The improved cavity model was been found to reproduce results in accordance with experiments.