This paper presents ‘Pick-A-Mood’ (PAM), a cartoon-based pictorial instrument for reporting and expressing moods. The use of cartoon characters enables people to unambiguously and visually express or report their mood in a rich and easy-to-use way. PAM consists of three characters that each express eight different mood states, representing four main mood categories: energized-pleasant (excited and cheerful), energized-unpleasant (irritated and tense), calm-pleasant (relaxed and calm), and calm-unpleasant (bored and sad). The added value of PAM compared to existing instruments, is that it requires little time and effort of the respondents, which makes it suitable for design research applications, which are often used in situations in which people have little time or motivation to report their moods. Mood is defined, a brief review of existing instruments is provided, and the development and validation of PAM is reported. Various design (research) applications are presented, illustrating that PAM can be used both as a tool for measurement (i.e. to enable researchers to measure the moods of their respondents) and as a tool for communication (i.e. to enable people to communicate their mood in social interactions).