Blends of poly-epsilon-caprolactone (PCL) and poly-beta-hydroxybutyrate (PHB) were prepared by mixing the two polymers in the presence of dicumylperoxide (DCPO) in solution of chlorobenzene. Similarly blends were obtained by mixing the two polymers with no peroxide added. The blends were prepared in a break of composition, from 85% wt PHB/15% wt PCL to 15% wt PHB/85% wt PCL, respectively. Also pure polymers were reacted with DCPO in the same way of the blends. Thermal (DSC), spectroscopic, mechanical (tensile tests) and morphological (SEM) analyses were performed on the blends and on the pure polymers. Significant differences were found in the chemical-physical characteristics of the blends with and without peroxide.