Values of the Landé g factors are obtained for the first time for rovibronic levels of the (3d)J ¹Δ _g ^- state of the D₂ molecule and of the (4d)S ¹Δ _g ^- state of the H₂ and D₂ molecules. Semiempirical values of these quantities are obtained for the first time for the (4d)R ¹Π _g ^- state of the H₂ molecule and the (3d)I ¹Π _g ^- and (4d)R ¹Π _g ^- states of the D₂ molecule. These values are determined in terms of the nonadiabatic model, which takes into account the interaction between the ndπ¹Π _g and ndδ¹Δ_g (n = 3 and 4) states in the approximation of pure precession, with the use of the semiempirical values obtained by us for the expansion coefficients of wave functions in the adiabatic basis functions and the results of our numerical calculation of overlap integrals of the vibrational wave functions of these states. The values thus obtained are in good agreement with the data available in the literature. It is found that the interference effects of coupling of the ndπ¹Π_g and ndδ¹Δ_g states lead to significant perturbations of the dependences of the g factors of vibronic levels on the rotational quantum number as compared to the adiabatic results. These perturbations are regular (reaching a factor of nine) for the I ¹Π _g ^- and R ¹Π _g ^- states and irregular (reaching a factor of 50) for the J ¹Δ _g ^- and S ¹Δ _g ^- states. The nonadiabatic values of g factors obtained in our previous studies for the H₂, HD, and D₂ molecules in the i ³Π _g ^- and j ³Δ _g ^- states are improved by an additional inclusion of adiabatic effects. It is established that the effect of the electron spin on the g factor values for rovibronic levels of the 3dΔ _g ^- states is significant and reaches 25% for H₂ and 130% for D₂.