Method for measuring the concentration of a gas component in a measurement gas by means of a gas analyzer, in which - for the purpose of wavelength-dependent scanning of a gas component absorption line of interest, the wavelength of the light of a wavelength-tunable light source is varied within periodically consecutive scan intervals and is additionally modulated in the process with a frequency (f 0), - the modulated light is guided through the measurement gas onto a detector, - a measurement signal generated by the detector is demodulated in the event of a harmonic (nf 0) of the frequency (f 0), and - a measurement result is produced by fitting a desired curve to the profile of the demodulated measurement signal, characterized in that - a function orthogonal to the desired curve is provided, and an orthogonal component (M ortho) of the measurement result is produced by fitting the orthogonal function to the profile of the demodulated measurement signal, - for the purpose of measurement calibration given a known concentration of the gas component to be measured, an interfering parameter is varied and there is determined in the process an error which consists of an inphase component (N in), in the form of the difference between the obtained measurement result (M in) and a desired measurement result (S in), and of the orthogonal component (M ortho) a relationship between the inphase component (N in) of the error and its orthogonal component (M ortho) further being determined, and - in the case of the measurement of an unknown concentration of the gas component the measurement result (M in) obtained in the process is corrected with an inphase component which is determined, with the aid of the relationship determined in the measurement calibration, from the likewise obtained orthogonal component (M ortho). - for the purpose of wavelength-dependent scanning of a gas component absorption line of interest, the wavelength of the light of a wavelength-tunable light source is varied within periodically consecutive scan intervals and is additionally modulated in the process with a frequency (f 0), - the modulated light is guided through the measurement gas onto a detector, - a measurement signal generated by the detector is demodulated in the event of a harmonic (nf 0) of the frequency (f 0), and - a measurement result is produced by fitting a desired curve to the profile of the demodulated measurement signal, - a function orthogonal to the desired curve is provided, and an orthogonal component (M ortho) of the measurement result is produced by fitting the orthogonal function to the profile of the demodulated measurement signal, - for the purpose of measurement calibration given a known concentration of the gas component to be measured, an interfering parameter is varied and there is determined in the process an error which consists of an inphase component (N in), in the form of the difference between the obtained measurement result (M in) and a desired measurement result (S in), and of the orthogonal component (M ortho) a relationship between the inphase component (N in) of the error and its orthogonal component (M ortho) further being determined, and - in the case of the measurement of an unknown concentration of the gas component the measurement result (M in) obtained in the process is corrected with an inphase component which is determined, with the aid of the relationship determined in the measurement calibration, from the likewise obtained orthogonal component (M ortho).