In reinforced concrete design, the concrete in the tensile zone is assumed to be ineffective and increase the dead load of the structure. In order to reduce the selfweight of reinforced concrete beam, this paper examines the flexural performance of reinforced concrete beams containing lightweight and normal weight concrete. The lightweight concrete was made from waste polystyrene. Four reinforced concrete beams were prepared with different depth of lightweight concrete. The control beam B1 consists of normal concrete. In Beams B2, B3 and B4, the depth of lightweight concrete was 25%, 50% and 75% of the total depth of the beam measured from the bottom surface respectively. The beams were subjected to four-point bending test and was loaded in increments until failure. At each load increment, the central deflection was determined. The propagation of cracks and the mode of failure were monitored. As the depth of lightweight concrete increases, the failure load decreased. The presence of lightweight aggregate tends to cause a brittle failure. In addition, the mode of failure for reinforced concrete beams containing lightweight concrete was shear failure. Keywords: cracks, lightweight, load defelection, structural performance, waste