Seed storage of agricultural crops in the conditions of International Space Station (ISS) is an effective method of quick plant breeding aimed to enhance the adaptability, and improve the biologically active compound accumulation and crop yield. Biochemical and mineral composition (ICP-MS) of lettuce grown in greenhouse from seeds stored for one year at the ISS was assessed. High varietal differences in lettuce tolerance to the effect of micro-gravity and radiation were evaluated using the values of yield, biometrical parameters, antioxidant status and plant mineral composition. Among the cultivars studied, i.e. Petrovich, Synthesis, Moskovsky parnikovy, Picnic, Cavalier and Bouquet, only the cvs. Retrovich, Synthesis, Moskovsky parnikovy and Picnik retained seed viability. Significant yield increase was recorded for the cv. Moskovsky parnikovy, while the cvs. Petrovich, Synthesis and Picnic demonstrated a tendency to the yield decrease. Improvement of photosynthetic pigment accumulation due to seed space storage was recorded for the cv. Moskovsky parnikovy and, particularly, the latter cultivar differed from the other cvs. due to the significantly higher proline level and lower MDA levels in leaves. Though space stress did not cause any significant decrease in antioxidant accumulation of plants, the latter demonstrated valuable changes in mineral composition. Among the 23 elements tested, V, Se. Fe and Cr showed higher concentrations compared to those in the control plants. Positive correlations between Ca, Sr, Cd, Cp, Mg, Mo and Pb were recorded (r > 0.9; p < 0.001).