Background and Objective: To comprehensively examine comorbidity in unselected cohorts of patients with depression, stroke, multiple sclerosis (MS), Parkinson's disease/parkinsonism (PD/PKM), dementia, migraine, and epilepsy. Methods: This cross-sectional study used morbidity data recorded by Dutch general practitioners. Index disease cohort sizes ranged from 241 patients with MS to 6,641 patients with lifetime depression. Thirty somatic and seven psychiatric disease categories were examined to determine whether they were comorbid with the index diseases by performing comparisons with age- and gender-matched control cohorts. Identified comorbidities were classified as either "possible" or "highly probable" comorbidity. Results: An extensive range of 26 disease categories was found to be comorbid with lifetime depression. The comorbidity profile of stroke was also wide, including 21 disease categories. The comorbidity patterns of migraine and epilepsy comprised each 11 disease categories. Those concerning MS, PD/PKM, and dementia included a small number of disease categories. Conclusion: This study provides comprehensive knowledge of the occurrence of somatic and psychiatric comorbidity in general populations of patients with depression, stroke, MS, PD/PKM, dementia, migraine, and epilepsy. The implications of the findings for clinical practice and research are discussed.