Background: Among all other causes of meningitis Tuberculous meningitis (TBM) is an endemic disease in developing countries with an incidence of 7 to 21%. But the available methods of diagnosis of TBM have too low sensitivity and specificity. In these situations, Adenosine Deaminase (ADA) estimation has been found to be profoundly useful as it is less time consuming, cost effective and affordable. Aims and objective: To evaluate the diagnostic significance of cerebrospinal fluid (CSF) adenosine deaminase (ADA) activity in tubercular meningitis (TBM) in children. Materials and methods: In Our Study, 200 consecutive medical ward in–patients of Pediatrics department Patna medical college, Patna who had features of meningitis were prospectively enrolled and included in the study after informed consent. Results: Out of 200 patients 112 were males and 88 were females. Cases of tuberculous meningitis constituted 34% of the study group and bacterial and viral meningitis were 22% and 23% respectively. while 21% patients from study group had no any type of meningitis. CSF ADA cut–off of 10 U/L considered in our study has 100% sensitive and 97.06% specific. Conclusion: detection of elevated level of ADA in CSF in suspected cases of meningitis in children will be a guide in the diagnosis of TBM so that early treatment will be started and will lead to improved outcome