The purpose of the present study was to determine the working length using electronic apex locator in various intracanal mediums and cone beam computed tomography scan and to compare the lengths with the actual length of the tooth. Methods: In an in vitro setting, a total of 45 primary molar roots were decoronated till the cemento enamel junction for standardization, working length was measured with the Apex DSP (Septodont, France) at the ‘apex’ in presence of three different irrigating solutions namely 0.9 % saline, 0.2 % chlorhexidine and 2.5 % sodium hypochlorite. The radiological working length was then calculated with cone beam computed tomography scans. The collected data was analyzed using descriptive statistics. Independent‘t’ test was done to compare the working length between the groups. Results: Findings showed there was significant difference in working length determination using apex locator in presence of saline and chlorhexidine when compared to sodium hypochlorite. Also working length determination with cone beam computed tomography compared to actual length did not show any significant difference. Conclusion: Apex DSP can be considered to be accurate across a variety of irrigants commonly used in the pediatric endodontic practice. A CBCT scan can be used as a diagnostic tool for pulpal treatment when treating multiple carious lesions.