Selenium (Se) is a beneficial element for plant although at high concentrations, it is toxic and causes in plant growth retardation. The most important biological role of Se is in association with activity of GPX enzyme. This enzyme protects plant cells against environmental stresses such as salinity. Salinity is one of the most important environmental stresses in most soils of Iran. Therefore, it is necessary to investigate interaction of salinity and Se on growth, yield and antioxidant capacity of plants under saline conditions. This study was carried out to investigate interaction of salinity and Se on growth, yield, activity of GPX (as an index of plant antioxidant capacity) in roots, and some concentrations of selected micronutrients. Wheat is a strategic crop and the most important cereal in the world. Lettuce is also one of the most consumable vegetables by the people particularly in our country. This study was performed in two individual trials. Each experiment was set up in a completely randomized factorial design in triplicates at Soilless Culture Research Center. Treatments were four levels of selenium (0, 20, 40 and 150 µM in the form of Na 2 SeO 4 ), two salinity levels (0 and 100 mM NaCl). Two wheat genotypes ( Triticum aestium cvs. Kavir and Back Cross-Rushan) were used in the first trial and two lettuce cultivars ( Lactuca sativa L. Black Saladine and White Tourist) were used in the second trial. The effect of selenium on the growth and yield of wheat varied based on the crop genotype. Salinity significantly decreased root and shoot dry matter yield of both wheat genotypes studied. The highest root activity of GPX in wheat was found at the 40 µM Se level. Iron concentration in the roots of wheat was increased with increasing Se concentration in the nutrient solution while shoot Fe concentration was unaffected by Se addition. Concentration of Cu in roots and shoot of wheat was decreased with increasing Se concentration from 20 to 150 µM. Selenium addition had no significant effect on shoot Zn concentration in wheat. Except for concentration of Fe in the roots, concentrations of other nutrients measured in the roots and shoot were decreased significantly by salinity. The highest Fe uptake by roots of wheat was achieved at the 150 µM Se level while shoot Fe content was decreased by increasing Se in the nutrient solution. In both wheat genotypes, translocation of the studied elements from roots to shoot was higher at non-saline conditions compared with saline conditions. Two lettuce cultivars varied in their response to Se application. Salinity and Se addition reduced root dry matter yield of lettuce. Shoot dry matter yield of lettuce at the 40 µM was higher than that in the other Se levels. “Black Saladine” produced the lowest shoot dry matter yield at the 150 µM Se level. In this genotype, the highest root activity of GPX was found at the 150 µM Se level. For “White Tourist” cultivar, the highest