Purpose: to study the diametrically opposite approaches in judicial and expert practice to determine the mass of the drug d-Lysergide (LSD, LSD-25), which consist in the possibility of: a) establishing its (mass) in "pure form"; b) taking into account the paper carrier. The methodology is based on the dialectical method of cognition, as well as the synthesis and generalization of empirical and theoretical material. Conclusions: it has been established that the use of solvents inevitably results in the resulting extract containing, in addition to the narcotic, other components (e.g., dyes) present on the surface of the paper fragments or embedded within the paper. Furthermore, since forensic centers lack reference samples of d-lysergide (LSD, LSD-25), it is virtually impossible to objectively resolve the mass determination task under consideration.