CsLnMnSe3 (Ln = Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Y) and AYbZnQ3 (A = Rb, Cs; Q = S, Se, Te) have been synthesized from solid-state reactions at temperatures in excess 1173 K. These isostructural materials crystallize in the layered KZrCuS3 structure type in the orthorhombic space group Cmcm. The structure is composed of LnQ6 octahedra and MQ4 tetrahedra that share edges to form 2∞[LnMQ3] layers. These layers stack perpendicular to  and are separated by layers of face- and edge-sharing AQ8 bicapped trigonal prisms. There are no Q-Q bonds in the structure of the ALnMQ3 compounds so the formal oxidation states of A/Ln/M/Q are 1+/3+/2+/2-. The CsLnMnSe3 materials, with the exception of CsYbMnSe3, are Curie-Weiss paramagnets between 5 and 300 K. The magnetic susceptibility data for CsYbZnS3, RbYbZnSe 3, and CsYbMSe3 (M = Mn, Zn) show a weak cusp at approximately 10 K and pronounced differences between field-cooled and zero-field-cooled data. However, CsYbZnSe3 is not an antiferromagnet because a neutron diffraction study indicates that CsYbZnSe3 shows neither long-range magnetic ordering nor a phase change between 4 and 295 K. Nor is the compound a spin glass because the transition at 10 K does not depend on ac frequency. The optical band gaps of the (010) and (001) crystal faces for CsYbMnSe3 are 1,60 and 1.59 eV, respectively; the optical band of the (010) crystal faces for CsYbZnS3 and RbYbZnSe3 are 2,61 and 2,07 eV, respectively.