Abstract: In this paper, the permutation group D'_n(n) and appropriate graph counting series are used to obtain generating function which is used to enumerate constitutional isomers of substituted cycloalkanes and homo-loges of cycloalkanes.The cycle index of D'_nh(2n) group is revised so that it can be used to enumerate chiral and achiral cycloalkanes.An alkyl configuration partition, then, is defined, and a simple method finding the numbers of isomers of homologs of cycloalkanes is given.Some numerical results are tabulated.