Photoconduction mechanism of a polyimide with an alicyclic diamine, PI(PMDA/DCHM), prepared from pyromellitic dianhydride (PMDA) and 4,4＇-diaminodicyclohexylmethane (DCHM) was investigated. Its UV absorption spectra, fluorescence spectra, photoconductivity, and annealing effects on the photocurrent generation were measured and compared to those of CPD, N,N＇-dicyclohexylpyromellitic diimide, and PI(PMDA/DMDHM) prepared from PMDA and 3,3＇-dimethyl-4,4＇-diaminodicyclohexylmethane (DMDHM). Photoconductivity of PI(PMDA/DCHM) depends upon the degree of molecular packing between polymer backbones. PI(PMDA/DMDHM) has no photoconductivity, probably due to a barrier to their intermolecular packing by the existence of two methyl substituents. Photoconductivity of PI(PMDA/DCHM) would be the result of the weak intermolecular interaction formed by mixed layer packing arrangement between pyromellitic moiety of one polymer backbone and N-cyclohexyl ring of another one in the ground state : Radiation absorption of this weak intermolecular interaction immediately forms a charge-transfer complex in the excited state and produces radical cation and anion charge carriers, which lead to the photoconductivity in the bulk polyimide film of PI(PMDA/DCHM).