Structural and optical properties of relaxed and pseudomorphic ZnCdSe/ZnSe quantum well heterostructures are described. Structural quality and strain conditions of the films are linked with their light emission properties. From the temperature dependence of photoluminescence (PL) spectra we estimate exciton coupling constants to acoustic phonons in pseudomorphic and relaxed structures. The coupling is noticeably weaker in strain-relaxed structures with strong localization effects. PL kinetic studies confirm strong localization of excitons in strain-relaxed structures.