This paper overviews the efficiency of the European carbon market EU-ETS (European Union Emission Trading System or Scheme) connected with projects JI (Joint Implementation) and CDM (Clean Development Mechanism). As known, these three flex mechanisms enable industries to earn emission reduction credits to be traded on the market. The aim of this paper is to highlight some relevant problems such us price volatility, environmental integrity, financial tools, etc., present since the Kyoto Protocol came into force in 2005. These aspects are here fully debated. The conclusion supports the idea that the CDM and JI projects have little connection with the principle of environmental sustainabilit
