Targeting drugs or pharmaceutical compounds to tumor site increases cancer treatment efficiency and therapeutic outcome. Nanoparticles are unique delivery systems for site-targeting within an organism. Many novel technologies have been established in drug research and development area. Nanotechnology now offers nanometer size polymeric nanoparticles and these particles direct drugs to their targets, protect drugs against degradation, and release the drug in a controlled manner. Modification of nanoparticle surface by molecules leads to prolonged retention and accumulation in the target area of the organism. Current efforts of designing polymeric nanoparticles include drug activation in the target area, controlled drug release at the site upon stimulation, and increased drug loading capacity of drug polymer conjugates. Recent progress in molecular mechanism elucidation of cancer cell and rising research in nanoparticle designs may provide efficient cancer treatment modality and innovative nanoparticle designs in the near future.