Stöber (Behav Res Ther 36:751–756,
1998) asserts that worry is characterized by reduced concreteness of thought that interferes with successful emotional processing via reduction of imagery. Extant research has not examined concreteness of thought during a period of idiographic worry, nor has it directly compared concreteness during worrisome thinking to concreteness during other types of repetitive negative thinking such as depressive rumination. We sought to test Stöber’s theory as it relates to idiographic periods of worry, and further examined its applicability to periods of depressive rumination. Consistent with Stöber’s theory, we found that worry and depressive rumination were significantly and non-differentially more abstract than was baseline mentation. Contrary to Stöber’s theory, concreteness of thought was not related to degree of reported imagery during either worry or depressive rumination. Theoretical and clinical implications of these findings are discussed.