Suicide is a complex and challenging human phenomenon, and, although knowledge is expanding concerning its risk factors, its background is still not fully understood. There is currently an increasing interest in genetic factors associated with suicide, since these may lead to the emergence of personality traits and temperaments that may be long-term predictors of suicidal behaviour. One of the most likely genetic candidates in the background of suicide is the 5-HTTLPR polymorphism of the serotonin transporter gene. This review focused on papers published on the association of the 5-HTTLPR polymorphism of the serotonin transporter gene and suicidal behaviour as well as research on possible endophenotypes related to suicide. Although there are contradictory results, several studies and meta-analyses support the idea that the S allele plays a role in the background of violent suicide. However, in order to be able to delineate the genetic background of suicide, different types of suicidal behaviour should be distinguished, since studies indicate that these may have different genetic factors. Also, personality traits and temperaments should be identified that may play a modulating role between genetic factors and suicidal behaviour. So far, neuroticism, affective temperaments, and impulsive aggression have been found to be associated with both the S allele and suicidal behaviour. This study aimed to integrate findings concerning possible endophenotypes modulating between genetic factors and manifested suicidal behaviour.