Introduction: Differential diagnosis between angiotensin converting enzyme inhibitors (ACEi) angioedema (AE) and idiopathic histaminergic AE (ihAE) is often challenging. Follow-up data may help discriminate these conditions but are scarcely reported. Our objective was to report on the follow-up of patients with suspected ACEi-AE and to describe the baseline characteristics of AE attacks in patients with a diagnosis confirmed by follow-up. Methods: Sixty-four patients with suspected ACEi-AE (i.e. with exposure to ACEi before first attack, no urticaria associated and normal C1-inhibitor levels) and at least one follow-up visit were included. Data were retrospectively collected at baseline and during follow-up. Results: After follow-up, the diagnosis of ACEi-AE was confirmed in only 30 patients. The remaining patients were reclassified as ihAE (21 patients) or undetermined-mechanism AE (13 patients). In ACEi-AE patients, attacks occurred mostly in men (61%) with a median age of 64 (interquartile range 17) years old, with a highly variable delay from ACEi introduction (23103 months), and preferential involvement of lips (50%), tongue (47%) and throat (30%). Patients with confirmed ACEi-AE frequently reported classical histaminergic features, such as history of allergy and atopic conditions (20%), attacks with preferential evening onset (25%) and spontaneous resolution <24h (26%). ACEi-AE attacks responded to icatibant (79%). Conclusion: A final diagnosis of ihAE is frequent in patients with an initial suspicion of ACEi-AE; and follow-up should be systematically performed to ascertain the diagnosis in this population. Baseline clinical features seem insufficient to accurately discriminate between ACEi-AE and histaminergic AE, highlighting an unmet need for diagnostic biomarkers.