The appearance of cavum septi pellucidi (CSP) has been already connected with developmental disorders or with serious psychiatric diseases (schizophrenia, maniac-depressive disorder, aggressiveness or similar). During our investigation of CSP, group of alcoholics seemed to be interesting for investigation and comparison with the groups of schizophrenics and people with violent behavior. We obtained CSP in 205 out of 670 fixed brains (429 male and 241 female) of persons aged from 14 to 89 (mean +/- SD: 53.28 +/- 16.57), 85 cava belonged to our group of interest. Prevalence of CSP in aforementioned groups was significantly higher than in the rest of examined population. Only in the group of 20 to 39 years of age all kinds of obtained pathologies were present. Alcoholics with CSP suffered from cardiovascular diseases and died accidentally and aggressive persons were the only drug addicts in our examined group and they had the shortest life span. 34 out of 41 schizophrenics had no data about prior diseases and disorders and they were the ones who committed suicide frequently. Intensive demyelinization of corpus callosum and transformation of potential space between laminae of septum pellucidum to the actual one could explain the CSP appearance among alcoholics. To our opinion, cavum septi pellucidi might be used as an additional marker of organic brain changes in long term alcohol abuse, as a consequence of demyelinization due to lipolytic effect of ethanol, and lower cerebral blood flow.