Background: Several studies have demonstrated that bipolar Ⅱ (BD-Ⅱ) disorder represents a quite common, clinically and biologically distinct form of major mood disorders that should be separated from bipolar Ⅰ (BD-Ⅰ) disorder.The aims of this cross-sectional study were to assess temperament and clinical differences between patients with BD-Ⅰ and BD-Ⅰ disorders, and to assess whether temperament traits are good predictors of hopelessness in bipolar patients, a variable highly associated with suicidal behaviour and ideation.Methods: Participants were 216 consecutive inpatients (97 men and 119 women) with a DSM-Ⅳ-TR diagnosis of BD who were admitted to the SantAndrea Hospitals psychiatric ward in Rome.Patients completed the Temperament Evaluation of Memphis, Pisa, Paris and San Diego-Auto questionnaire (TEMPS-A), the Beck Hopelessness Scale (BHS), the MINI (Mini International Neuropsychiatric Interview), and the Gotland Scale of Male Depression (GSMD).Results: BD-Ⅱ patients had higher scores on the BHS (9.78±5.37 vs.6.87±4.69; t143.59=-3.94; p<0.001)than BD-Ⅰ patients.Patients with higher hopelessness (compared to those with lower levels of hopelessness) reported more frequently moderate to severe depression (87.1% vs.38.9%; p<0.001) and higher MINI suicidal risk.Hopelessness was also associated with the individual pattern of temperament traits.Conclusion: Temperaments are important predictors both of suicide risk and psychopathology and may be used in clinical practice for better delivery of appropriate care to bipolar disorders patients.