The preparation of cross-linked polyethylene with high energy electrons is a well-known and used method to change material properties. A new developed technique called "Electron induced reactive processing" (EIReP) combines polymer modifica-tion with high energy electrons and melt mixing processes. In the case of polyeth-ylene, this novel technique leads to exceptional mechanical properties. Definitely, these properties depend on the molecular architecture as well as the morphological characteristics of polyethylene after the electron treatment. In this work we concentrate on the morphological changes of high density polyeth-ylene generated by using state of the art high energy electron treatment in the solid state compared with high density polyethylene modified with the electron induced reactive processing in the dynamic melt. The characterization of the morphology and the dispersion of different crystalline regions within modified and unmodified polyethylene were performed by several microscopic techniques such as optical microscopy with a polarization filter and hot stage as well as transmission electron microscopy. DSC measurements were used to evaluate the crystallinity as well as the temperatures of melting and crystallization. XRD investigations were applied for calculation of crystallinity, evaluation of size of crystallites and for estimation of long period of the crystalline lamellae. Keywords: process controlled morphologies, nanostructures, electron microscopy