Abstract The primary goal of this study was to apply an innovative analytical method based on a gas membrane sensor (GMS) to quantify the concentrations of CO 2 and CH 4 gas in water columns from volcanic lakes. For this purpose, dissolved CO 2 and CH 4 from the Monticchio Grande and Piccolo (Mt Vulture, Italy) and Pavin (Massif Central, France) lakes, characterized by depths of 35, 38 and 92 m, respectively, were measured using two different approaches: GMS and SH (single hose), the latter being an independent conventional method. The CO 2 and CH 4 concentrations recorded via the GMS and SH techniques were within the analytical errors of the two methods. These test measurements demonstrated that the GMS method can be successfully used to produce highly accurate in situ measurements of dissolved gas composition along the vertical profiles of lakes.