The thermal decomposition of several Mo(VI)- and Mo(V)-complexes with salicylaldehyde S-methylisothiosemicarbazone (H2L) of general formula Mo(VI)O-2(L), Mo(VI)O-2(L)S (S = MeOH, EtOH, Py, DMF, DMSO), (Mo(V)O(HL)Cl)(2)O and (Mo(V)O(HL)Cl)(2)O.Me2CO were investigated. These complexes and the previously prepared Mo(VI) complexes were characterized by spectroscopic (IR, UV-VIS, NMR) and thermal (TG, DTG and DSC) methods. The molar conductivity and magnetic susceptibility of the complexes were also determined. Structure of some decomposition products were determined and a decomposition schemes were proposed.