Field experiments and survey were carried out at the northern coast of the Kaliningrad Peninsula and the Kursh spit together with bathymetric measurements and sediments analysis at the offshore zone in order to study the coastal morpho- and lithodynamics. Contrary to general opinion the Kursh spit appeared to be not a spit, created by longshore drift, but a coastal bar due to deposits transversal movement (from the sea floor). The conclusion is drawn of primary importance for the coast protection measures planning and realisation.