In spectral extinction particle sizing technique, an inversion method in the dependent model is proposed, in which the commonly used particle size distribution functions are retrieved using the modified beta function as the assumed type of distribution function. The feasibility and reliability of this inversion method are investigated, and the inversion using the Johnson's S-B function as the assumed type of distribution function is also discussed for comparison. Simulation experiments indicate that the commonly used monomodal particle size distribution functions can be retrieved well using the modified beta function as a versatile function in the dependent model with the spectral extinction data. This inversion method not only overcomes the difficulty caused by the inability to determine the type of specified distribution function accurately beforehand, but also allows the description of different types of distributions by a single model. (C) 2008 Elsevier B.V. All rights reserved.