Objective: To compare diagnostic value of bone marrow aspiration and bone marrow trephine in reaching to final diagnosis. Study Design: Cross Sectional Descriptive study. Setting: Pathology Department of Khyber Teaching Hospital, Peshawar. Period: December 2015 to September 2016. Material & Methods: About 199 bone marrow procedure were done during study period. Nine cases were excluded because their trephine biopsy specimen was not available. So, the remaining 190 cases, of both the sexes and age above 2 years were included. Bone marrow aspiration and trephine biopsy were obtained from all the patients, and examined. Qualitative data was determined by frequency and percentages. Quantitative data was shown by mean and standard deviation. Results: 190 cases were included in the study. The mean age of the sample was 40 ±11.5 SD years (range: 2 to 81 years). Bone marrow aspirate alone could diagnose 139 (72.8%) cases while trephine biopsy alone was sufficient to diagnose 12 (6.3%) cases. Both the modalities showed similar diagnosis in 39 (20.9%) cases. Conclusion: Leukemias, anemias, and idiopathic thrombocytopenic purpura can be diagnosed by marrow aspiration alone. Aplastic anemia and myelofibrosis need marrow trephine for diagnosis. Both these modalities are important lest any diagnoses should be missed.