We undertook a project to develop a psychometrically sound instrument measuring adolescent sun-related behavior for use in the evaluation of a social marketing program. During the preliminary stages, we conducted a pilot study to test the face validity of the instrument with adolescents. Think-aloud sessions were completed with 24 adolescents. Results identified gaps in our understanding of adolescent sun-related behavior. Adolescents interpreted 'tanning' as specifically lying at the beach in the sun, however also reported behaviours to 'get a bit of sun', suggesting adolescents and researchers have different interpretations of key terms. The study highlights that use of the think-aloud technique can improve understanding behaviours of the target market and improve the validity of measures of adolescent sunrelated behaviour.