So far, scientific literature has paid attention to the cognitive and environmental determinants of presence, trying to offer a definition and assessment measures that could seize such an elusive concept. However, the emotional determinants of presence have received less attention. Emotional responses could play a key role in generating and enhancing presence, specially for some Virtual Reality (VR) applications, such as mental health field (both for promotion and treatment goals). The main goal of EMMA project -an European Community funded research project (IST-2001-39192)- is to study the relationships between presence and emotions. In particular, after analyzing the possible emotional impact of high compelling synthetic experiences characterized by a high level of presence, the EMMA project wants to develop "mood devices" able to induce different forms of mood enhancement.