Abstract: The invention relates to a method for determining concentrations of absorbing gases by means of a spectroscopic measuring device, wherein wavelength-dependent measurement values for a light intensity are obtained and a wavelength-dependent measurement value function is represented based on these values. A wavelength-dependent theoretical function is defined, which includes as parameters a calibration parameter and the concentrations. The calibration parameter is defined as a function of a device parameter and a correction parameter that depends on the concentrations.