On purpose to examine the effect of branch length on the miscibility of polyolefin blends, miscibility behavior of linear polyethylene/poly(ethylene-co-1-octene) blend was studied and compared to that of linear polyethylene/poly(ethylene-co-1-butene) blend. Miscibility of the blend was determined by observing the morphology quenched from the melt, and by using the relation between interaction parameter and copolymer composition. When the weight composition and molecular weight was the same, poly(ethylene-co-1-octene) was slightly more miscible with linear polyethylene than poly(ethylene-co-1-butene) was. (c) 2007 Wiley Periodicals, Inc.