Objective: Continuous performance tests are known to typically measure sustained attention but usually also yield parameters that potentially measure other subprocesses of attention. The aim of the present study was to test the factor structure of the Conners's Continuous Performance Test (CCPT) in a heterogeneous clinical sample consisting of subjects considered to fail in different subfunctions of attention. Method and Results: CCPT records from 376 patients were factor analyzed, yielding five factors indicating a differentiation between focused attention, hyperactivity-impulsivity, sustained attention, vigilance, and change in control. Conclusion: The study warns against reducing CCPT performance to one overall score of attention. The study further emphasizes the need to reserve the concept of sustained attention for measures of change as a function of time on task. The differentiation between sustained attention and vigilance and the concept of change in mental control during the test are possible methodological contributions of the study. (Contains 3 tables.)