Using ps transient and cw photoinduced absorption and photoluminescence, and their respective versions of optically detected magnetic resonance, we elucidate the origin of photoexcitations in thin films of poly(phenylene acetylene) (PPA). We clearly identified two kinds of photoexcited singlet excitons : the first type is radiative and unrelaxed whereas the second type is nonradiative, self trapped and thus long-lived. Other photoexcitations such as triplets and polarons play only a minor role in PPA.