Four series of random graft copolymers with stilbenoid side chains on a polystyrene (PS) backbone were synthesized, and their optical properties were compared with blends of a series of model compounds in PS. The graft loading (5, 15, and 25 mol %), the type of link to the polymer backbone ("ether" or "direct"), and the number of methoxy groups substituted on the stilbene moiety were systematically varied. Absorption, emission, and time-resolved photoluminescence (PL) properties are presented for the compounds in solution and as spin-coated films, and relative quantum yields have been determined. Mixed monomer/excimer emission was found to be the characteristic emission for all grafts, while the reversibility of the excimer formation seems to vary for the different grafts. In the blends the miscibility of the model compounds is quite different: the 4-methoxystilbene/PS system readily forms aggregates and crystallites, whereas the 3,4,5-trimethoxy-4'-methylstilbene/PS system forms uniform mixtures showing excimer-type emission. The PL efficiencies decreased with concentration in all cases where excimeric emission was found. For the blend containing 4-methoxystilbene, however, the PL efficiency increased with concentration.