Positron annihilation spectroscopy (PAS) has been used to study the depth profile (0 - 8 µm) in coating systems of polymer in the presence of titanium dioxide(TiO2) under different exposure of UV irradiations. Doppler broadening energy parameters of annihilation radiation show a systematic variation with the time of UV irradiation and with the TiO2 structure and particle size. The nano-layer and interfacial structures and free-volume properties of coatings are obtained. Positron annihilation lifetime results provide additional information about free-volume size and distribution in pigmented coating systems. Recent progress in the investigation of pigmented coatings using positron annihilation and slow positron beam will be presented.