A two year field study was carried out to know the impact of cultivars selection and nitrogen on growth and development of cotton (Gosssypium hirsutum) plant under semi arid conditions of Punjab, Pakistan. Nitrogen and cultivar selection plays an important role in determination of plant yield under various environmental circumstances. It is the basic constituent of plant green material and in nature. Various treatments of nitrogen were Zero, 60, 110 and 160 kg ha-1 applied in splits to the soil along with high yielding cotton cultivars (CIM-496, CIM-506, and CIM-534). The highest significant vegetative quality traits of cotton i.e. plants main stem height, nodes per plant were produced by the cultivar CIM-534 during 2007 and 2008. However, physiological parameters like leaf area index (LAI), crop growth rate (CGR), relative growth rate (RGR) and net assimilation rate (NAR), reproductive parameters such as total dry biomass (TDM), cotton bolls count m-2 and seed cotton yield were produced significantly the maximum by CIM-496 cultivar. Vegetative, reproductive and physiological traits were directly proportional to the increasing N rates ha-1. For better yield and yield components, nitrogen given at the rate of 160 kg ha-1 proved to be the optimum under semi arid conditions.