Depression is one of the leading causes of disability and is efficiently treated by antidepressant pharmacotherapy. Pharmacological treatment is still hampered by a delayed time of onset of clinical improvement and a series of side effects. In elderly, it is complicated by an increased risk of adverse drug events, associated with age-related physiological changes, individual variability in drug metabolism mainly related to polymedication, concurrent diseases and diet. Then every physician would like to predict these impairments and to prescribe a "tailored" treatment based on individual characteristics. One of the tools for this tailored medication is the use of pharmacogenetics, leading to an evaluation of the human genome implications in the treatment response (efficacy, time of onset and adverse events). Some candidate-genes have already been identified, showing encouraging results, but only a few studies focus on depressed old subjects. The existing studies have analyzed the polymorphism of the metabolizing enzyme gene CYP2D6 and the serotonin transporter genes implications. The results are promising but more researches are necessary to include pharmacogenetic studies in the clinical practice.