The O-substitute derivatives of isoflavans were examinated and the results of the structural and conformational analysis of the molecules were given in this study. Isoflavanes are active compouds of plants and vegetables. Isoflavanes have diverse effects on human and animal health. They show preventative properties on growth of breast cancer cells. In addition to this, they affect women's health during menopause and reduce the risk of fibroids and endometriosis. Soy and red clover are natural sources of isoflavanes. In this study, we have studied on isovestitol and sativan which are isoflavanes. Their structural and electronic properties have been studied in theory via the molecular mechanics (MM+ force field) and the semi-empirical self consistent-field molecular-orbital (AM1) calculations. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were computed with density functional theory (DFT) and ab initio (HF) methods with the 6-31G basis set which were performed by using Gaussian 03 and HyperChem 7.5 program package.