Results of the theoretical conformational analysis using molecular mechanics and ab initio techniques for the tetrathia-crown ethers 1,4,7,10-tetrathiacyclododecane ([12]aneS(4)) and 1,4,8,11-tetrathiacyclotetradecane ([14]aneS(4)) are presented. MM3 was used for conformational searching using two schemes, and ab initio calculations with the 6-31G** basis set were carried out for die lowest energy minima. Importance of the quality of conformational searching is illustrated. 1,2-dithiomethoxethane and 1,3-dithiomethoxypropane are studied to better understand conformational properties of the macrocyclic ligands.