The present invention concerns a method and system for gas concentration measurement of gas or gas mixtures dissolved in liquids. A gas or gas mixture dissolved in a liquid sample is extracted from the liquid sample using an extraction system and conducted into a measurement chamber. Then a measurement signal is generated by means of a radiant source and the measurement signal is directed to a measurement object in a measurement chamber containing the gas or gas mixture to be measured. The measurement signal is filtered using at least two wavelengths, whereupon the filtering is preferably implemented by means of an electrically tunable, short-resonator Fabry-Perot interferometer. Then the filtered measurement signals are detected my means of a detector.