In spectral measurements, a consequence of using finite bandwidth is that the observed quantity is the convolution of the instrument-spectral-bandpass Junction with the unknown quantity that we want measure. To know the true value of the quantity to he measured, we must perform a deconvolution of the observed data. This article proposes a deconvolution technique based on the complete knowledge of the instrument-spectral-bandpass function and on the hypothesis that the unknown quantity to be measured can be power expanded locally around each measuring wavelength. Typical spectral bandpass functions, triangular and Gaussian and with symmetric and asymmetric shape are considered. The spectral resolution evaluated by simulation as a function of the bandwidth and of the spectral scanning step is given to represent the performance of this technique. (C) 2009 Wiley Periodicals, Inc. Col Res Appl, 35, 334-342, 2010; Published online 29 October 2009 in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20552