Worry involving repetitive thoughts about threats and concerns is prevalent when confronted with a life-threatening illness such as cancer. Worry may contribute to the formation of negative cognitive representations of illness that can have a detrimental effect on behavioral and adaptive outcomes. The study examined for the first time (a) the relationship between worry and early formation of cognitive representations of illness in individuals with suspected lung cancer over the presurgical and postsurgical period and (b) associations between worry and anxiety, sex, age, and educational level. Correlational statistical analyses were used to assess worry and cognitive representations in 42 individuals before lung surgery and again 3 weeks postsurgery. Higher worry was significantly related to more threatening content in multiple illness domains. Repeated-measures analysis of variance using high- and low-worry strata showed significant interactions between worry and time on certain illness domains indicating that high worry was associated with increased threat and negative contents in cognitive representations of illness over time. Multiple regression analyses showed that trait anxiety was the only significant predictor of worry in a regression model including age, sex, education, and anxiety before surgery. Findings suggest that higher worry at time of diagnosis is associated with the development of negative and more threatening contents in cognitive representations of illness in individuals with suspected lung cancer.