This paper focusess on the effect of cooling profile on the crystallization behaviour of polyethylene blends, and how by varying the crystallization conditions the co-crystallization region will change. Temperature rising elution fractionation (TREF) technique was used for fractionate the polymers and blends. Each of the TREF fractions was studied using both Differential scanning calorimetry (DSC) and Crystallization Analysis Fractionation (CRYSTAF) to determine whether the fraction contained both types of materials. It is shown that the difference in the crystallization fractionation mechanisms between DSC, CRYSTAF and TREF can be exploited to study co-crystallization effects in polyethylene blends. Results also show that by varying the heating and cooling profiles in DSC and CRYSTAF, the co-crystallization fractions will be a single fraction or as two separate fractions. The results show a unique visual illustration of any co-crystallization regions in the blends as well as how much the crystallization conditions effect the blend crystallization