Cognitive style is thought to be a stable marker of one's way to approach mental operations. While of wide interest over the last decades, its operationalization remains a challenge. The literature indicates that cognitive styles assessed via i) questionnaires are predicted by personality and ii) performance tests (e.g., Group Embedded Figures Test; GEFT) are related to general intelligence. In the first study, we tested the psychometric relationship between the Cognitive Style Index questionnaire (CSI) and personality inventories (NEO Five Factor Inventory; NEO-FFI, HEXACO Personality Inventory Revised; HEXACO-PI-R). In the second study, we assessed the CSI, NEO-FFI, GEFT and a general intelligence test (Raven's Standard Progressive Matrices Test; RSMT). We found that CSI scores were largely predicted by personality and that CSI was uncorrelated with GEFT performance. Instead, better performance on the GEFT was associated with better performance on the RSMT. We conclude that i) cognitive style questionnaires overlap with personality inventories, ii) cognitive style performance tests do not measure cognitive styles and should not be used as such and iii) the cognitive style concept needs to be assessed with alternative measurement types. We discuss possible future directions.