The article deals with the problem of recoverable gas reserves. The analysis of the development of gas and gas condensate elds of the Predverkhoyansk and Vilyui oil and gas bearing regions is made. For the Ust-Vilyui gas eld, a signi cant overestimation of the initial gas reserves approved by the USSR State Reserves Committee was shown. The nal gas recovery factor for the main reservoir III-A of the Ust-Vilyui gas eld was 0.56. For the Sobo-Khainsky gas eld, an assumption was made about insuf cient knowledge due to the location in the water area of the river. Vilyui and the existing negative experience in the development of the Ust-Vilyui eld. For the Mastakhskoye gas condensate eld, revaluations are given with a decrease in the initial balance reserves. It is shown that the high rate of gas production has become the most signi cant factor behind the low development ef ciency. The total nal gas recovery ratio for the depleted deposits of the Mastakhskoye gas condensate eld did not exceed 0.34 of the initial reserves calculated by the volumetric method and 0.55 of the reserves estimated by the pressure drop method. It was concluded that the most reliable in the conditions of a complex geological structure of deposits is the assessment of gas reserves by the pressure drop method. The idea is formulated that for the elds of the Vilyui syneclise, which have productive horizons with an initial low gas saturation of the reservoirs, the nal gas recovery coef cients can be estimated in the range of 0.55.