This paper reviews nanoparticles designed and prepared for cancer therapy and diagnosis, including inorganic nanoparticles, liposomes, lipid nanoparticles and polymeric nanoparticles. The nanoparticles are classified into (i) magnetite nanoparticles, (ii) other types of inorganic material-based nanoparticles that are generally used for imaging and hyperthermia treatment, and (iii) organic material-based nanoparticles for drug delivery, gene therapy and other applications. Their structures are analyzed, and the details of the components and the modes of bonding of the core, shell and surface are compared. In the final section, lipid nanoemulsion and chitosan nanoparticles developed by the authors for gadolinium neutron capture therapy of cancer are introduced; the design and preparation of these particles for the accumulation of active agents in tumors have been demonstrated. In all cases, nanoparticle targeting in the body is the most critical requirement for achieving excellent outcomes. This is common to chemotherapy, gene therapy, molecular imaging, etc. From a pharmaceutical viewpoint, it is emphasized that the macro biodistribution of active agents in the whole body has to be optimized and controlled; this is necessary in order to assure the clinical efficiency and safety of these agents before utilizing specific functions of biomolecules that have been discovered through molecular cell biology.