Abstract: Experiments of convective drying on thin slices (0.5 cm) of banana, cassava and pumpkin were carried out under three air temperatures of 85, 90 and 95°C at constant 2 m sec-1 of air velocity with and without application of infrared in the drying process. The drying characteristics included diffusion coefficient and activation energy were evaluated under the influence of the infrared radiation. Tutuncu model was used in order to evaluate the effective diffusion coefficient and activation energies of samples under different values of parameters of temperature and infrared conditions during drying. The results indicate that the effective diffusion coefficients increased with increasing of the air temperature and increase in the infrared radiation. The diffusion coefficient values were found to be between 1.85x10-9 to 7.02x10-9 m2 sec-1 for banana, 1.18x10-9 to 6.16x10-9 m2 sec-1 for cassava and 1.12x10-9 to 3.64x10-9 m2 sec-1 for pumpkin respectively for lowest temperature of 85°C and no infrared radiation to highest temperature of 95°C and highest infrared of 200 W. The activation energies were found to be between 15.89-19.75 kJ mol-1 for banana, 26.44-32.85 kJ mol-1 for cassava and 27.83-29.26 kJ mol-1 for pumpkin respectively for the same condition.