Molecular imaging technology can be used for many applications, including drug development, clinical investigations, and diagnostic techniques. Molecular imaging techniques depend upon molecular mechanisms operating in vivo. This imaging technique encompasses the visualization, characterization, and measurement of biological processes at the molecular and cellular levels in humans and other living systems. This technology uses the radiopharmaceuticals, intended for human use, which should be sterile, pyrogen-free, safe, and efficacious for specific indications. Nuclear medicine imaging methods or radionuclide imaging methods include positron emission tomography (PET), single photon emission computed tomography (SPECT) and hybrid imaging. Contrast to anatomical imaging, nuclear medicine techniques can provide physiological imaging and high sensitivity and specificity at sub-millimolar levels. This review aims to definite examples of radiopharmaceuticals which are used in molecular imaging with information of radiation, radioactivity, and radionuclide production. The radiopharmaceuticals like Technetium-99m (Tc-99m),