Asian Americans (AAs) and Native Hawaiians/Pacific Islanders (NHs/PIs) are the fastest growing segments of the US population. However, their population sizes are small, and thus AAs and NHs/PIs are often aggregated into a single racial/ethnic group or omitted from research and health statistics. The groups' substance use disorders (SUDs) and treatment needs have been under-recognized.We examined recent epidemiological data on the extent of alcohol and drug use disorders and the use of treatment services by AAs and NHs/PIs.NHs/PIs on average were less educated and had lower levels of household income than AAs. Considered as a single group, AAs and NHs/PIs showed a low prevalence of substance use and disorders. Analyses of survey data that compared AAs and NHs/PIs revealed higher prevalences of substance use (alcohol, drugs), depression and delinquency among NHs than among AAs. Among treatment-seeking patients in mental healthcare settings, NHs/PIs had higher prevalences of DSM-IV diagnoses than AAs (alcohol/drug, mood, adjustment, childhood-onset disruptive or impulse-control disorders), although co-morbidity was common in both groups. AAs and NHs/PIs with an SUD were unlikely to use treatment, especially treatment for alcohol problems, and treatment use tended to be related to involvement with the criminal justice system.Although available data are limited by small sample sizes of AAs and NHs/PIs, they demonstrate the need to separate AAs and NHs/PIs in health statistics and increase research into substance use and treatment needs for these fast-growing but understudied population groups.