Experiencing emotional distress is the number one reason why people who are undergoing behaviour modification (e.g. quitting smoking, dieting) suffer from relapses. Providing emotional support is an effective way to help them overcome the unpleasant effects of negative affect and adhere to their regimen. Building computers with such ability has grabbed the attention of the HCI community in recent years. Early research has shown some promising results when adopting strategies of how we comfort others, but many questions on how to build such systems remain unanswered. This paper presents the results of a 2 (modality: animated vs. no visual) by 3 (intervention: non-empathy vs. empathy vs. empathy and expressivity) between-subjects study that investigates the impact of two important factors and their interaction in the design of such systems: (1) different ways of expressing empathy, and (2) the modality of delivering such content. Findings and implications for the design of empathic comp...