In the study of interpenetrating polymer networks (IPN)-like systems consisting of polyethylene (PE) and butyl methacrylate (BMA)-styrene (S) copolymer PE/(BMA-co-S), the effect of the crosslinker on the morphology of IPN by using electron microscopy and atomic force microscopy (AFM) was investigated. The IPN-like system PE/(BMA-co-S) represents a two-phase system with finely dispersed domains of crosslinked PE matrix. The interphase between dispersed domains and PE matrix is inhomogeneous and is considered the most interpenetrated part of this IPN-like system. The size of the domains decreases with the content of crosslinker used. The AFM micrographs allowed the observation of PE lamellae with lengths of about 25 nm.