Organosoluble polyimide (PI)/ceramic composite films with different BN or (BN + AlN) contents were under investigation for their thermal conductive performances. The chosen polyimide constituted by 4,4′-oxydiphthalic dianhydride/2,2-bis(3-amino-4-hydroxyphenyl)hexafluor opropane could be dissolved and cast into thin films at room temperature. The commercially available BN and AlN fillers up to a volume ratio of 0.6 were added to the polyimide and their thermal conductive performances were measured. BN powders needed a surface precoating treatment to avoid sedimentation. The dense and flexible PI/BN composite films, after a drying treatment at 200°C, showed high thermal conductivity of 2.3 W/m·K−1 at a BN volume ratio of 0.6, as compared with 0.13 W/m·K−1 for pristine polyimide. However, in the case of PI/(BN + AlN) composite films, thermal conductive performance degraded because the films became highly porous at the higher AlN content. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers