Abstract: Two varieties of Zea mays (L.) from Iran differing in their growth and development have been used to study the effect of water and nitrogen stress on some of their photosynthetic performance. Chlorophyll content and fluorescence, photosynthetic CO2 assimilation of leaves and total leaf water potential were measured. The results indicated that photochemical efficiency of photosystem II (Fv/Fm) was severely reduced by nitrogen and water deficiency. Whereas, leaves of low-nitrogen plants had earlier and more prolonged reduction in Fv/Fm compared to leaves of high-nitrogen grown plants of the same water treatment. Chlorophyll content and photochemical efficiency of photosystem II as the key parameters determining photosynthetic were reduced in KSC 108 and 301 cultivars. KSC 301 was able to perform better, because showed higher Fv/Fm ratios when subjected to water stress. Net photosynthetic rates and total leaf water potential were lower in the leaves of the nitrogen deficit treated plants under water stress. The rates of net photosynthetic assimilation were decreased during drought in both varieties, but KSC 108 was more affected. The results showed that although rewatering ameliorated reduction in Fv/Fm and net photosynthetic rates, not completely eliminate depression in these parameters for low nitrogen grown plants.