Background: Cyclothymic temperament (CT) is a more or less ‘permanent’ instability of mood, thinking and activity (behaviour), which is frequent in bipolar disorders. Testing the impact of age on CT items, as has been done in many mood disorders, could further define its features. The aim of the study was to test the relationship between age and CT items. Methods: During follow-up visits in a private practice, 209consecutive remitted bipolar II (BP-II, n = 138) and major depressive disorder (MDD, n = 71) outpatients were re-diagnosed by a mood disorder specialist psychiatrist, using the Structured Clinical Interview for DSM-IV (blind to patients), and self-assessed CT was evaluated by the TEMPS-A questionnaire (blind to interviewer). Results: Mean (SD) age was 39.1 (10.0) years (median 39, range 16–63 years). BP-II had significantly more CT items. Logistic regression tested the association between each CT item and age. Of the 17 CT items, 8 showed a trend (p < 0.10) or significant association with age. Among these items, there were items suggested to be core features of CT, i.e. instability of mood and energy: ‘moods and energy either high or low’, ‘constantly switching between being lively and sluggish’ and ‘being sad and happy at the same time’. However, other CT items related to mood and energy instability, i.e. ‘sudden shifts in mood and energy’ and ‘mood often changing for no reason’, were not significantly associated with age. Discussion: Study findings suggest that age may have an impact on some CT items related to mood and energy, which might become more common with age (according to the item’s wording), and that many CT items may not be impacted by age, suggesting more stability.