Thin films of CdSe nanoparticles were chemically deposited on a glass substrate. The PL spectra of these films are dominated by a red-IR emission band, associated with the recombination of shallow trapped electrons and deep trapped holes. The optically detected magnetic resonance (ODMR) measurements revealed that the trapping sites have low symmetry, thus suggesting their existence at the surface of the nanoparticles. Moreover, the theoretical simulation suggests a distribution of e-h pair distances, leading to an ensemble of exchange interaction values. The trapping sites are distributed around the circumference of the nanoparticles, and the e-h spatial separation is therefore limited by the size of the nanoparticles. The g values of the trapped carriers are substantially different from those of the band edge, further supporting the idea of trapped carrier localization at imperfection sites.