The concept of post-COVID syndrome (PCS) as an independent nosological entity underlies the search for criteria for establishing this diagnosis. To date, there is an idea of two clinical phenotypes of the post-COVID state, occurring with different pathogenetic mechanisms. One of them is probably the consequences of damage to organs and systems and / or iatrogenic factors suffered during COVID-19. The pathogenesis of the other is not entirely clear, and the clinical manifestations are like those of a number of dysfunctional pain disorders, such as fibromyalgia (FM) and chronic fatigue syndrome / myalgic encephalomyelitis. The article is devoted to the analysis of literary data indicating the similarity of PCS and FM. The need to revise the diagnostic criteria for PCS is substantiated.