Abstract Background:The discrimination of pleural thickening from minimal pleural effusion may be difficult as both lesions appear as anechoic on grayscale ultrasound, hence, free of ‘‘echoes’’ does not confirm the presence of pleural fluid. Aim of this study:To evaluate the value of color Doppler ultrasound in differentiating minimal pleural effusion that could be aspirated from pleural thickening and to compare it with grayscale ultrasound. Patients and methods:This analytic cross-sectional study was done prospectively on 40 patients who presented with pleural based opacity in their chest radiographs compatible with minimal pleu-ral effusion. Gray scale ultrasound was done for all patients then color Doppler ultrasound exam-ination was applied to detect the presence or absence of fluid color sign. The presence or absence of pleural effusion was confirmed by aspiration of pleural fluid. Results:The sensitivity of real time gray scale ultrasound in detecting minimal pleural effusion and differentiating it from pleural thickening was 95.5% while, specificity was 33%, and accuracy was 67%. The ability of ultrasound in discrimination of minimal pleural effusion from pleural thickening improved greatly by application of the color Doppler examination where the specificity of the method reached 100% while the sensitivity was 91% and accuracy was 95%.