The aim of this study is to use the FAO-56 single and dual crop coefficient approaches to estimate actual evapotranspiration (ETa) over irrigated citrus orchard under drip and flood irrigations in Marrakech, Morocco. The results showed that, by using crop coefficients suggested by FAO-56 paper, the performance of both approaches was poor for two irrigation treatments. The Root Mean Squared Error (RMSE) between measured and simulated ETa values over irrigated citrus under drip irrigation was about 1.43 and 1.27 mm/day for the single and dual approaches respectively, while the corresponding statistics for the citrus irrigated by flooding technique was 1.87 and 2.48 mm/day. After the determination of the appropriate values of the crop coefficient (Kc) based on eddy covariance measurements of ETa, the performance of both approaches greatly improved. The obtained values of crop coefficient were below than the FAO-56 values by about 20%. The low Kc values obtained reflect the practicing of drip irrigation for one field and the low value of cover fraction for the other field. Additionally, the efficiency of the irrigation practices was investigated by comparing the measured Kc for two fields. The results showed that an important amount of water was lost by direct soil evaporation on citrus orchard irrigated by flooding technique. Key words: Crop coefficient, drip and flood irrigation, evapotranspiration, FAO-56 model, irrigated citrus.