Two field experiments were carried out at the Agric. Exp. Sta. Fac. Agric., Cairo Univ., Giza, during 2009 and 2010 seasons to study the response of three hybrids of maize, Zea mays L. (S.C. 10, S.C. 122 and T.W.C. 321) to  four plant densities (4.76 plants/m², 5.56 plants/m², 6.67plants/m² and 8.33 plants/m²) on yield and yield components. Results showed that, significant differences between maize hybrids in plant height, number of ears/plant, barren %, LAI, number of kernels /row, grain weight/ear and grain yield/plant in both seasons.  Number of rows per ear, number of ears/plant, number of kernels per row, weight of grains/ear, seed index, shilling percentage and grain yield/plant decreased significantly and gradually by increasing plant densities from 4.76 plants/m² to 8.33 plants/m². Plant height, barren %, LAI and grain yield per hectare significantly increased by increasing plant densities from 4.76 plants/m² to 8.33 plants/m². The highest grain yield/ha (9.96 and 10.32 ton/ha) were obtained by planting 8.33 plants/m² in 2009 and 2010 seasons. The lowest 7.88 and 8.28 tons/ha were recorded by planting 4.76 plants/m² in 2009 and 2010 seasons, while planting 6.67 plants/m² and 5.56 plants/m² were intermediate in grain yield/ha. Increasing plant density from 4.76 plants/m² to 8.33 plants/m² increased grain yield/ha by 25.70 and 24.98 % in 2009 and 2010, respectively, while this increase was 11.09 and 8.05 % for plant density of 6.67 plants/m² in 2009 and 2010 seasons. The effect of the interaction between hybrids differences and plant density treatments on yield and yield components are not significant in most studied characters except number of ears/plant, LAI and grain yield/plant.