Psychological factors have long been suspected to influence lung function in asthma. While earlier experimental research has demonstrated the susceptibility of the airways to suggestion, only recent studies have investigated the impact of various emotional states and stressful challenge on the airways in health and asthma. We reviewed studies from the last 15 years that have used experimental emotion and stress induction techniques or longitudinal diary observations to explore these influences. Findings suggest that unpleasant emotional states are associated with a decline in lung function in health and asthma. Changes are usually small on average, but usually reach clinical significance in a subset of patients. Pleasant emotional states are also sometimes associated with a lung function decline, suggesting a susceptibility of the airways to arousal in general. From longitudinal studies, more evidence for effects of both pleasant and unpleasant states is available, but also highly idiosyncratic associations between mood, stress, and lung functions were observed. While initial findings indicate the importance of specific autonomic, ventilatory, and immunological pathways for emotion-induced lung function changes, more research is needed on these underlying mechanisms.