Lattice-mismatch induced defects have been studied by means of deep-level transient spectroscopy (DLTS) in two types of GaAs-based heterostructures, GaAs/InGaAs and GaAs/GaAsSb, and in a GaN-based laser-diode heterostructure grown on a bulk GaN substrate. DLTS measurements, carried out with p-n junctions formed near the heterostructure interfaces, revealed three deep-level traps in the investigated structures, which have been related to dislocations on the grounds of their logarithmic kinetics for capture of charge carriers into the trap states. An electron trap at $E_{\text C}-0.64$ eV and a hole trap at $E_{\text V}+0.67$ eV, found in the GaAs-based structures, have been attributed, respectively, to threading and misfit dislocations. An electron trap at $E_{\text C}-0.23$ eV, found in the GaN-based structure, has been tentatively related to dislocations in a p-type layer of the structure. Detailed investigation of the dependence of DLTS-line amplitude and its shape on the filling time of the traps with charge carriers allowed us to specify the type of electronic states associated with the traps.