Structural features of solid solutions based on CaYb2S4 (the Yb3S4 structural type) are studied using the methods of Rietveld full-profile analysis, measurement of pycnometric density, and thermal analysis in vacuum with simultaneous study of variation of the elementary cell parameters. Conductivity of samples with different doping additive content are studied in the medium of argon and in the hydrogen sulfidecontaining medium using the impedance technique. Different mechanisms of defect formation are analyzed as dependent on the doping degree.