Results of extensive quantum-chemical modeling of the gas phase reactions during CVD of group 13-15 materials from inorganic and organometallic precursors are summarized. Importance of the association reactions in the gas phase under CVD conditions is emphasized. Ring and cluster compounds serve as gas phase intermediates in the CVD of group 13 metal nitrides. Hydrogen-containing species are predicted to have higher importance as precursors for the stoichiometry controlled CVD processes. Binary pnictides of group 13 metals are prospective materials for high-power high frequency electronic and optoelectronic devices. 1 One of the commercially most important ways to synthesize 13-15 compounds is the chemical vapor deposition (CVD) techniques. Usually group 13 halides or organometallic derivatives R 3 M and group 15 hydrides YH 3 are used as source compounds. Despite the extensive experimental investigations, thermodynamic studies of possible oligomer intermediates of CVD processes are rather rare. Yet less is known about their gas-phase behavior. Knowledge of thermodynamic properties is important for understanding and optimizing selective growth processes. 2 It should be noted, that the detailed mechanism of the CVD process is yet unknown. Recently, a general scheme of CVD process which includes both dissociation and association pathways (Figure 1), has been proposed. 3 In such a situation, when experimental investigations in situ are very demanding, quantum-chemical approach allows one to obtain consistent set of structural and thermodynamic data. This approach recently has been used for number of case studies of 13-15 CVD processes, 4-6 and potential cyclic precursors. 7 In the present report results of recent quantum-chemical studies 3,4,8-11 of group 13-15 donor-acceptor adducts R 3 MYH 3 , daughter cycle and cage compounds (see Figure 1) are summarized.