Hybrid solid electrolyte films consisting of poly(ethylene oxide) (PEO), LiClO4, a mixture of ethylene carbonate (EC) and gamma-butyrolactone (BL) and poly(acrylonitrile) (PAN) were examined in order to obtain the best compromise between high conductivity, homogeneity and dimensional stability. Measurements of electrical conductivity and differential scanning calorimetry have been carried out. When the ratio of LiClO4/(EC/BL) is large, the electrolyte films are completely amorphous at room temperature and in the other cases, they are partially crystalline. The materials having higher EC/BL content are more likely to be a gel-electrolyte than a plasticized PEG-salt electrolyte. The Li+ ions in these films seem to migrate primarily through the solvent domains as in the gel-electrolytes. The highest room temperature conductivity of 2.0 x 10(-3) S cm(-1) is found for a film of 31PEO-9LiClO(4)-50EC/BL-10PAN. This film has a similar conductivity value as compared with PAN-based gel electrolytes, but with a better dimensional stability.