Background: Phantom tumour or Vanishing tumour stands for a localized transudative interlobar collection of pleural fluid in congestive heart failure. It is named so because of the resemblance to a tumour on the CXR and its tendancy to disappear following therapy for cardiac failure. It was first reported by Stewart in 1928 as ‘’interlobar hydrothorax ‘’. Case report: A 80 year old man presented Shortness of breath and swelling over legs generalized tiredness and dry cough since five days. He had no history of Tuberculosis nor any other co-morbidities On Examination he had clubbing of fingers, B/l Pitting Pedal Edema along with raised JVP. Chest was barrel in shape. Bilateral fine inspiratory crepitations were present in Lower Lung Fields. No Cardiac Murmurs were audible. Chest x ray PA View showed sharply demarcated oval homogenous dense shadow about 3x4 cm size in the Right Middle Lobe. USG Thorax was done and showed fluid in the interlobar fissure. Echocardiography was done and showed Left Ventricular Hypertrophy, Global Hypokinsia of Left Ventricle with LVEF of 45%, Mild Tricuspid Regurgitation, jerky septum in motion. Parenteral diuretic therapy was started along with fluid restriction. After five days of therapy repeat chest X rays revealed significant resolution of homogenous opacity with only thin strip of opacity of 0.5cm was remaining. Conclusion: This case confirms efficacy of the conservative medical treatment (loop diuretics and fluid restriction) for the localized interlobar effusion in congestive heart failure. Phantom lung tumor should be considered and excluded in any patient presenting with clinical features of congestive heart failure with an apparent lung mass on a CXR. Finally, it is necessary to highlight the importance of recognizing this condition in order to avoid unnecessary, expensive, and possibly harmful diagnostic and treatment errors.