Thin layer drying characteristics of hazelnuts during roasting were described for a temperature range of 100-160 degrees C, using five semi-theoretical and two empirical thin layer models. The effective diffusivity varied from 2.301 x 10(-7) to 11.759 x 10(-7) m(2)/s over the temperature range. Temperature dependence of the diffusivity coefficient was described by Arrhenius-type relationship. The activation energy for moisture diffusion was found to be 1891.6 kJ/kg. Thin layer drying characteristics of hazelnut roasting were satisfactorily described by an empirical Thompson model with the linear temperature dependence. (C) 2000 Elsevier Science Ltd. All rights reserved.