A revised version of the CST was validated by comparing depressed patients with anxious patients, recovered depressed and anxious patients and normal controls. Other measures included three severity of illness scales (the Beck Depression Inventory, the Hamilton Rating Scale for Depression and the state version of the State-Trait Anxiety Inventory) and three well-established cognitive scales (the Automatic Thought Questionnaire, the Hopelessness Scale and the Dysfunctional Attitude Scale). Depressed patients were differentiated from normal controls on all subscales of the CST and the three other cognitive scales. They were similarly differentiated from recovered depressed patients, except for negative interpretations relating to the self when age was covaried. Anxious patients were significantly differentiated from depressed patients on total level of negative thinking, negative interpretations of unpleasant events and negative thinking relating to the world when age was covaried. Hopelessness and dysfunctional attitudes also differentiated depressed and anxious patients. Face validity and concurrent validity for the new scale are provided. The specificity of negative thinking to depression and the possibility of a vulnerable cognitive style are discussed.