Comparative study of Inconel 718 nickel-base superalloy produced by selective laser melting (SLM) and conventional technology was carried out. The SLM Inconel 718 microstructure consists of g grains, surrounded by d phase plates and small carbides. g¢¢ and g¢ precipitates were present within the g subgrains. The d phase plates are mainly located along grain boundaries like in conventional Inconel 718. The g grains consist of columnar and equiaxed subgrains. Study of microstructure showed that the columnar subgrains in their turn consisted of equiaxed subgrains. The SLM material features a developed substructure in g grains, and dispersed precipitates, oxides along subgrain boundaries. SLM Inconel 718 and conventional Inconel 718 were subjected to high pressure torsion (HPT), which resulted in microstructure refining down to nanocrystalline size and partial dissolution of Nb containing g¢¢ and d phases. d phase particles were revealed more clearly after subsequent annealing at the temperature close to aging temperature like in conventional superalloy. Nanostructure of SLM Inconel 718 formed by HPT had duplex (g + d) structure and was found to be thermally stable at 600 °C during 2 h. Annealing of the SLM Inconel 718 led to superior microhardness (956.46 HV), which was slightly higher than that of the conventional superalloy