Immiscible binary blends of poly(L,L-lactide) (PLLA), and poly(epsilon -caprolactone) (PCL), with 90/10, 80/20 and 70/30 wt% compositions, as well as ternary PLLA/PCL blends containing 0.5-5 wt% of a triblock PLLA/PCL/PLLA copolymer, were obtained by melt mixing using a twin screw extruder. Optical microscopy investigation of binary blends revealed the immiscibility of the components. The thermal behaviour of the blends was investigated by DSC and DMTA and compared with that of pure PLLA. The PLLA crystallization rate was enhanced in the presence of PCL domains. Morphological analysis of the cryofractured and etched-smoothed surfaces was carried out by SEM on both binary and ternary blends. A dimensional analysis of the PCL domains in binary and ternary blends was also performed in order to evaluate the influence of the presence of the triblock copolymer on the dispersion mode of PCL in the PLLA matrix.