Background: Molecular imaging is a new method of imaging of physiological studies at the cellular and sub-cellular levels. Among the various techniques that have been introduced for this purpose, magnetic resonance spectroscopy has provided an opportunity for study of brain activity and tumors in different areas of the body. Materials and Methods: In this review, using keywords such as MRS, Molecular imaging and Cancer at scientific databases such as PUBMED and ISI, studies in the field of MRS and related findings were evaluated. Results: MRS provides an opportunity to study brain disorders such as Alzheimer's and brain cancers. This method has also been used in diagnosis (between normal and cancerous tissues, different types of cancers and non-neoplastic from neoplastic), designing the most appropriate treatment regimen for each patient and also monitoring patient after treatment. Conclusion: MRS is a new method in molecular imaging that can be used in a variety of cancer diagnoses. This method can cover disadvantage of MRI procedure in evaluation of the tumor pathology.