Objectives: The purpose of this study is to evaluate Cortical Marrow Ratio (CMR) for reliability and relation to low Bone Mineral Density (BMD) in patients with femoral neck fractures. Methods: A total of 132 consecutive femoral neck fracture patients (median age 81.2 years, IQR 70.6-86.1) were assessed with DXA scans and digital hip x-rays. CMR was measured twice by two independent raters and analysed for reliability. CMR was then compared to BMD by means of a sensitivity/specificity analysis. Results: Using total hip BMD, 47 patients had a T-score ≤ -2.5 with a median CMR of 1.61(IQR 1.44-1.74), and 85 patients had a T-score > -2.5 with a median CMR of 1.89 (IQR 1.77-2.11). The ICC was 0.87-0.98 for intra-rater and 0.86-0.90 for inter-rater reliability. CMR showed a correlation coefficient of 0.58-0.59, a sensitivity of 72.3-76.6 % and a specificity of 75.3-76.5 % in relation to low BMD. Conclusions: CMR was found to be a highly reliable measure with acceptable sensitivity and specificity in relation to low BMD.