In the past two decades, the study of mood disorder patients using experience sampling methods (ESM) and ecological momentary assessment (EMA) has yielded important findings. In patients with major depressive disorder (MDD), the dynamics of their everyday mood have been associated with various aspects of their lives. To some degree similar studies have been conducted in patients with bipolar disorder (BD). In this paper we present the results of a systematic review of all ESM/EMA studies in MDD and BD to date. We focus not only on the correlates of patients' everyday mood but also on the impact on treatment, residual symptoms in remitted patients, on findings in pediatric populations, on MDD/BD specificity, and on links with neuroscience. After reviewing these six topics, we highlight the benefits of ESM/EMA for researchers, clinicians, and patients, and offer suggestions for future studies. (C) 2012 Elsevier Ltd. All rights reserved.