Cognitive vulnerability is a key construct in the hopelessness theory’s etiological chain (Abramson, Metalsky, and Alloy, 1989 Psychological Review, 96, 358–372). Researchers have proposed three operationalizations of this cognitive vulnerability construct: traditional, weakest-link, and flexibility. A five-week longitudinal study was conducted to test whether the weakest-link and flexibility approaches exhibit incremental validity over the empirically supported traditional approach. Results showed that the weakest-link approach has extensive overlap with the traditional operationalization (correlation was .93), and does not exhibit incremental validity in a college sample. In contrast, the flexibility approach appears to represent a unique vulnerability construct. However, the flexibility construct did not account for unique variance in the prediction of depressive symptoms beyond that explained by the traditional operationalization. The implications of the results for conceptualizing and operationalizing cognitive vulnerability are discussed.