In this work, results obtained by blending different single-site based linear polyethylenes with different ethylene-l-alkene copolymers are presented. Several morphology maps are created, and phase separation in the blends is detected. The extent of phase separation is found to be significantly wider in both temperature and composition than reported earlier, and no closed loops of phase separation is observed. This might partly be explained from the more even comonomer distribution found in single-site materials compared to materials made by other processes. The type of short chain branches is found to be of limited (if any) importance to the extent of phase separation while a difference in molecular weight of the blend components seems to affect the extent of phase separation. Furthermore, in blends containing butyl branches, the extent of phase separation is found to be reduced if the amount of comonomer is reduced. (C) 2001 Elsevier Science Ltd. All rights reserved.