The hydrogen adsorption on surfaces and on defect sites of ZnO nanoparticles (NPs) has been studied by using Raman and Fourier transform infrared spectroscopic methods. The presence of hydrogen at defect sites bound to zinc vacancy with different coordinations has been confirmed. To further identify the existence of isolated V-Zn and H-V-Zn complexes in the ZnO NPs, coincidence Doppler broadening (CDB) spectroscopic studies have been performed with respect to the CDB spectra of a 99.9999% pure Al single crystal. The broad momentum dip rho (L) showed between 15-17 x 10(-3) m(0)c suggests the trapping of positrons with the core electrons of 3p Zn. However, positron annihilation takes place between rho (L) 20-25 x 10(-3) m(0)c and this may occur with an electron belonging to OH bonds (V-Zn-H-i-O). Here the lattice hydrogen H+ ion acts as a compensating centre, and it can bind with the V-Zn around the dislocation and stacking faults (SFs) core, which may produce the acceptor-type complex defect for p-type conductivity. Finally, the existence of SFs and dislocation defects, including edges and steps, was confirmed by transmission electron microscopy.