Depressive disorders have strong genetic components. However, conventional linkage and association studies have not yielded definitive results. These might be due to the absence of objective diagnostic tests, the complex nature of human behavior or the incomplete penetrance of psychiatric traits. Imaging genetics explores the influences of genetic variation on the brain function or structure. This technique could provide a more sensitive assessment than traditional behavioral measures in psychiatric studies. Imaging genetics is a relatively new field of psychiatric researches, and may improve our understanding on neurobiology of psychiatric disorders. In this review, current understanding in neurobiology of depressive disorders, especially imaging genetic studies on serotonin transporter will be discussed.