The findings of review of promising methods and techniques providing increasing effectiveness of degassing of coal seams containing methane in the process of their underground mining are presented. Based on the review findings, traditional methods and techniques of degassing were identified, the effectiveness of which is 12–25 %, as well as unconventional methods providing methane degassing of up to 40%. As a classification feature of the unconventional methods and techniques of gaseous methane liberation, a condition of decreasing pressure and increasing temperature of coal matrix containing solid gas hydrate has been adopted. The conditions for methane transition from gas hydrate to free gas taking into account actual mining and technogenic conditions of the mines have been identified. Given the difficulty of supplying additional thermal energy into a coal seam, as the main way to reduce pressure in the seam, unloading of the rock mass relative to the initial stress state, and disruption of coal and rocks in the course of transition from their elastic deformation to elastic-plastic and out-of-limit deformation are accepted.