Small-angle neutron scatterings have been measured for the molten state and the crystalline state of polyethylene (PE) blends between the fully deuterated high-density PE (DHDPE) and the hydrogeneous PE with various degrees of branching. Quantitative analysis based on the random-phase approximation has clarified that for both the blend samples of DHDPE/LLDPE(2) and DHDPE/LLDPE(3) the D and H chains are miscible in the molten state, where LLDPE(2) is a linear low-density PE with ca. 17 ethyl branchings/1000 carbon atoms and LLDPE(3) is that with ca. 41 branchings. This result allows us to speculate that the difference in the crystallization behavior between the DHDPE/LLDPE(2) blend (cocrystallization) and DHDPE/LLDPE(3) blend (phase segregation) is not determined by the chain aggregation state in the melt but is governed more significantly by the kinetic effect during the crystallization process from the melt, as already pointed out on the basis of the time-resolved small-angle X-ray scattering and infrared spectral measurements. The radius of gyration (Rg) of the chain has been evaluated from the SANS data for the molten state as well as for the crystalline state. Even for the samples crystallized slowly from the melt, the Rg was found to be nearly equal to that of the crystalline state, supporting the random-reentry-type chain folding model for the crystalline lamellae of the cocrystallized DHDPE/LLDPE(2) blend sample.