Background: Although problems in the differentiation between self and object are commonly encountered in clinical work with suicidal adolescents, empirical validation of this phenomenon is limited in the literature. The aim of this study was to use empirical methods to examine the differentiation between self and parental representations in suicidal inpatient adolescents. Methods: Ninety-six adolescents participated in the study: 32 suicidal inpatients, 32 nonsuicidal inpatients, and 32 healthy controls. The 3 groups were matched for sex, age, and education. All participants completed scales on self-object differentiation and suicidal tendencies. Results: Suicidal adolescents were found to be significantly different from both nonsuicidal psychiatric and healthy controls in negative self and parental descriptions (P < .001) but did not differ from the other groups when describing positive traits. Moreover, suicidal adolescents described themselves as being significantly less differentiated from both their father (P < .001) and mother (P < .01) in negative traits but not in positive traits, when compared to the 2 other groups. Conclusions: Suicidal adolescents have difficulties differentiating the negative aspects of the self from the negative aspects of their parents. These results emphasize the importance of object relations theory in understanding suicidal tendencies in adolescents. A model combining negative symbiosis and suicidal tendencies offers several therapeutic intervention strategies.