Segmented polyurethane (PUR) elastomers based on naphthalene-1,5-diisocyanate (NDI) are distinguished for the combination of high elasticity, excellent wear-resistance and good thermal stability, Investigations with the help of element specific imaging transmission electron microscopy (ESI-TEM) on technical NDI elastomers as well as model elastomers with molecularly uniform NDI/1,4-butane diol hard segments of defined length give informations regarding the microphase separation, the packing behaviour of the hard segments and morphological superstructures. Allophanate crosslinks within the hard segment domains have a strong influence on the morphology of NDI elastomers, whereby, for instance, the microphase separation and the formation of spherolitical superstructures is disturbed.