Comorbidity of substance use disorders with physical and mental disorders was investigated among 1249 consecutive psychiatric consultation patients admitted to six general hospitals in Finland. Of the patients 354 (28%) were diagnosed with substance use disorders (ICD-10), of which 22% were due to use of at least two different types of psychoactive substances. Alcohol dependence (117/226) in male patients and acute drug intoxication (49/128) at a similar rate as alcohol dependence (44/128) in female patients were the most common clinical conditions. With few exceptions, all substance use disorders were comorbid and in 63% of affected patients comprised a "triple diagnosis" (i.e., physical, mental, and substance use diagnoses concurrently). Poisonings and personality disorders in both sexes, digestive system diseases in men, and injuries in women were related to substance use disorders. Conclusions for service provision were: (1) the high level of co-occurrence of physical and mental disorders with substance use disorders calls for comprehensive, multi-disciplinary assessment of any substance use problems ascertained in psychiatric consultations; (2) poisoning with substance use involvement and mental comorbidity was the most common combined clinical condition justifying provision of addiction psychiatric emergency consultations in general hospitals; (3) polydrug use indicating severe problems and complex treatment needs should be identified; and (4) psychiatric referrals of patients with physical alcohol-related disorders should be ensured in general hospitals.