Four selection criteria; grain/plant (GN), anthesis-silking interval (ASI), yield efficiency (YE) and leaf area duration (LAD) were tested in selected plants of maize (Zea mays L.) Bohooth106. The experiment was applied for six consecutive seasons (2009-2011) on the farm of the Dept. of Field Crops Sci./College of Agric./Univ.of Baghdad. Plants of high grain coincided with the desired criterion were taken, selfed, and harvested for three selection cycles under 200 and 400 kg N/ha . Seeds of third cycle of each selection criterion were planted for panmixia .The resulted seeds were grown in a yield trial for evaluation under 60 and 80 thousands plant/ha in spring and fall seasons2011 .The results showed that plants under low nitrogen were selected for shorter ASI and longer green duration (LAD) increased leaf area index (LAI) by 7.6% and 5% for spring season and 24.5% and 7.8%for fall season ,respectively .Ear length increased by 25, 15, 18, 14% than original population for ASI and LAD for spring and fall season respectively. Rows number/ear increased by4.6% in fall seasons. Grain number/row increased by 29, 7, 20 and 7.6% for ASI and LAD in spring and fall season respectively. This increase was reflected as an increase in grain yield (93.15gm and 146,11 gm) in spring and fall season respectively. Selection cycles also affected =all selected plants under high nitrogen. (LAI) increased for GN, ASI, YE except LAD. Ear length increased by 9, 19, 5.5, 5.5, 28.59 and 5.6 for GN, ASI and YE respectively. Grains number/row increased from 29. 27 and 31.26 to 34.66 and 40.66 grain for ASI in both. seasons. Grain yield increased by 32.8, 28.5, 55.3 and 30% in spring and fall seasons for ASI,YE respectively Plant density 80thousandes plant /h caused to increase LAI, decreased ear length ,rows number/ear and grains number/row and grain yield (gm), in high and low nitrogen for both seasons. Selection under high and low levels of N led to improve individual plant performance for many field characters, that resulted in increasing the efficiency of plants that were selected under high and low levels of nitrogen. It is recommended to use these criteria for selection and to develop inbred that will be tolerant to low nitrogen and high densities.