Associate defect centers formed by zinc vacancies, V Zn, and substitutional group-VII or group-III impurity ions have been investigated by electron spin resonance in ZnS 1 − x Se x mixed crystals. These centers form deep acceptor states and are converted into a paramagnetic state by supplying a photo-excited hole. Apart from the V ZnS 3Cl and V ZnS 3Br cluster (halogen, A-center), which had been previously analysed in pure ZnS, the following clusters were analysed in detail: V ZnS 2SeCl, V ZnS 2SeBr, V ZnSSe 2Cl and V ZnSSe 2Br. For centers of the type V ZnS 2SeX, hyperfine interaction arising from the isotope Se 77 could be detected. Here, the unpaired hole is found to be strongly localized in an atomic 4 p-orbital directed towards the zinc vacancy. In centers of the type V ZnSSe 2X the unpaired hole's wavefunction must be described by an antibonding molecular orbital, centered at the two selenium sites. Selective quenching of the paramagnetic centers V ZnS 2X, V ZnS 2SeX and V ZnSSe 2X occured by illumination with near-infrared light, peaked at 1.4, 1.6 and 1.8 eV, respectively. The process is interpreted as a hole transfer into states close to the valence band edge.