In this study, a laboratory dryer was used for thin layer drying of treated and untreated plums, and the moisture ratios at any drying time were compared by 14 different mathematical models. The effect of drying air temperature and velocity on the coefficients of the best suited moisture ratio model were determined by the multiple regression method. Root mean square error (RMSE) and chi-square (chi(2)) were used for determination of the best suitable model. In addition to these statistical parameters, the modeling efficiency (EF) was also determined. According to the results, the Midilli et al. model is superior to the others for explaining the drying behaviour of treated and untreated plums. It is possible to predict the moisture content of the product with a generalised model showing the effect of drying air temperature and velocity with the range of 60-80 degrees C and 1.0-3.0m/s. The effective diffusivity was found to be between 1.197 x 10(-7) and 4.551 x 10(-7) m(2)/s for treated plums and between 1.179 x 10(-9) and 6.671 X 10(-9) m(2)/s for untreated plums. (c) 2005 Elsevier Ltd. All rights reserved.