Background: Clinical decision support systems (CDSS or CDS) are interactive computer programs, which are designed to assist physicians and other health professionals with decision making tasks.

The main purpose of modern CDSS is to assist clinicians at the point of care. This means that a clinician would interact with a CDSS to help determine diagnosis, analysis, etc. of patient data.

Material and methods: In this study to systematically review controlled clinical trials assessing the effectsof clinical decision support systems (CDSSs), through the Health System Researches (H.S.R) method, We searched Medline, EMBASE, EBESCO, Ovid, MEDLINE, SID and IRANMEDEX databases and searched JAMA and BMJ Journals too for publications from 1980-2010 by two English and Persian language.

Results: Forty five studies met our inclusion criteria. From 28 studies that addressed the role of CDSSs in Improving the quality of health care, 22 (78%) study were useful, and from 13 studies that addressed the reducing of medical errors, 11 (85%) found improvement with the use of a CDSS. finally, in reducing Inappropriate diagnostic and therapeutic practice all of the CDSSs in 8 studies were completely useful.

Conclusion: The use of CDSSs in clinical practices can improve the quality of health care, reduce the amount of Inappropriate diagnostic and therapeutic practice and decrease medical errors.