Purpose This study investigates the feeling of emptiness in patients with borderline personality disorder (BPD) and patients with eating disorder (ED) and its relationship with suicidal behaviour and childhood traumatic events. Methodology One hundred three BPD patients and 107 ED patients were assessed with the Feeling of Emptiness Scale (FES) and the Traumatic Experiences Questionnaire (TQ). Suicidal behaviour was assessed with a specific interview for frequency and intensity of suicidal behaviour. Results Significant differences were found between the different factors of the FES between BPD patients and ED patients. A significant relationship was observed between Factors 1 and 4 of the FES and suicidal behaviour scores in both groups. Traumatic experiences were more strongly related to Factors 1, 2 and 4 in BPD patients. Conclusions BPD patients and ED patients show similar scores in the global construct of feeling of emptiness. However, results suggest some qualitatively difference between the nature of feeling of emptiness in BPD and in ED. As expected, suicidal behaviour is most frequently in BPD patients, and is significantly associated with Factors 1 and 4 of the FES in both groups. Therefore, feeling of emptiness could be a predictor of suicidal behaviours in patients with emotional and behavioural instability.