It is noted, that great advantage of gas injection methods is the possibility of their implementation in wide range of geological-physical conditions and, also, together with other methods. Reviewed are basic types of pools with hard-to-recover reserves, which are defined depending on geological-physical and technogenous features. Presented are results of gas injection methods implementation at such pools, enabling to recommend gas injection methods as basic ones for development of main types of pools with hard-to-recover oil reserves.