BackgroundCyclothymia seems to be often associated with coexisting ADHD symptoms, although this comorbidity is understudied. Emotional dysregulation is a core symptom of both conditions. MethodsAdult subjects with cyclothymia were consecutively enrolled at the outpatient service of the Second Psychiatry Unit of the Pisa University Hospital (Italy). Screening for ADHD was performed using the Adult ADHD Self-Report Scale (ASRS). We analyzed differences in sociodemographic and clinical characteristics between subjects with and without ADHD symptomatology. ResultsOf the total sample of 107 subjects, 43 % screened positive for ADHD. ADHD+ subjects were significantly younger than ADHD- subjects, had a lower level of education, a higher prevalence of psychiatric comorbidity, and a more frequent family history for ADHD and alcohol use disorder. In addition, ADHD+ subjects scored higher than ADHD- subjects on the affective instability, negative emotionality, and emotional impulsivity subscales of the RIPoSt-40 questionnaire, as well as on the 40‐item version of Reactivity, Intensity, Polarity, and Stability questionnaire (RIPoSt-40) total score. They also showed a stronger association with the cyclothymic and depressive subscales of the Temperament Evaluation of Memphis, Pisa, Paris, and San Diego (TEMPS-M) scale. Limitationsthe small sample size, the cross-sectional nature of the study, the use of self-report questionnaires, and the use of a screening test to assess comorbidity with ADHD symptomatology. ConclusionsADHD symptomatology is very common in cyclothymic individuals, and emotional dysregulation blurs the diagnostic boundaries between the two disorders. Several clinical features suggest the need for systematic evaluation of ADHD in patients with cyclothymic disorder.