The stoichiometry of thermal decomposition has been studied for (I) : [Ni(4-EtPy)(4)(NCS)(2)] as a host complex as well as for its clathrates [Ni(4-EtPy)(4)(NCS)(2)].G where guest molecule G - toluene, (II) : T, (III) : o-xylene (o-X) and (IV) : p-xylene (p-X). The loss of volatile components proceeds in three steps (-2L, -1L, -1L) for I and in four steps (-G, -2L, -1L, -1L) for II, III and IV. DSC and X-ray powder measurements indicated a phase transition in all compounds under study. However, this process is overlapped by the escape of G in II and III. The differences in enthalpy changes are associated with different guest-host interactions in the particular clathrates.