Three series of new isomeric 4-, 3- and 2-pyridine containing 1,2,4-oxadiazoles have been investigated via DSC and optical microscopy. DSC and microscopy investigations are mostly in good agreement and show that the transition temperatures and type of mesophases strictly depend on the nature and the length of the substitutent in the oxazolic part of 1,2,4-oxadiazoles and on the position of the heteroatom in the pyridine substituent. The mesomorphic properties of the compounds under study were compared with analogous 1,2,4-oxadiazoles, containing only carbocyclic units.