Introduction: This study was to identify the best accessible electronic information resources for finding answers to clinical questions in Iranian National Medical Digital Library.

 Methods: 20 clinical questions were randomly selected from four areas: prevention and treatment, diagnosis, etiology and prognosis from American National Library of Medicine (NLM). The keywords were searched in information resources such as Cochrane Database of Systematic Review (CDSR), ACP Journal Club (Ovid EBMR), Up to Date, and BMJ Clinical Evidence. Descriptive statistics was used for data analysis.

Results: The answering capability of these resources to clinical questions was different. Up To Date provided answers to %85, BMJ to %35, CDSR to %30, and ACP to %15 of the questions, respectively. Precision of retrieved information by these systems was 0.29 for CDSR, 0.24 for BMJ, 0.06 for ACP, and 0.02 for Up To Date. The highest number of answers to questions categorized in the aforementioned sections was provided by Up To Date whose low precision led to the retrieval of irrelevant information (%97). ACP showed less capability in answering to questions and could reply to questions about treatment and prognosis more than other areas.

Conclusion: Up To Date was the best source in answering the clinical questions however, when considering the quality of information, further research in this field is suggested.