Zinc Oxide nanoparticles in the size range of ~18 - 23 nm are prepared using wet chemical method. Hydrogen concentration in the samples was obtained by drying the precipitate at various temperatures. XRD pattern showed a single phase wurzite structure for ZnO nanoparticles. Average crystallite sizes and lattice parameters determined from XRD pattern showed a gradual increase with increasing dry temperature, while the lattice strain showed the opposite direction. Optical studies revealed the optical gap ranging from 3.05 - 3.24 eV. Hydrogen incorporation in the specimen was studied using infrared absorption measurement. Infrared absorption measurements revealed six hydrogen-related local vibrational modes in the wave number range from 2800 to 3600 cm–1. To remove hydrogen, some samples were annealed up to 800°C. Infrared absorption measurements showed that the local vibational modes disappeared. This shows that the observed local vibrational modes are due to the presence of hydrogen. The results of XRD and optical studies will be correlated with the results obtained from infrared absorption measurements.