Abstract : The large difference between the Planck scale and the electroweak scale, known as the hierarchy problem, is addressed in certain models through the postulate of extra spatial dimensions. A search for evidence of extra spatial dimensions in the diphoton channel has been performed using the full set of proton-proton collisions at sqrt(s) = 7 TeV recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. This dataset corresponds to an integrated luminosity of 4.9 /fb. The diphoton invariant mass spectrum is observed to be in good agreement with the expected Standard Model background. 95% confidence level lower limits of between 2.52 TeV and 3.92 TeV are set on the Ms scale in the context of the model proposed by Arkani-Hamed, Dimopoulos and Dvali, depending on the number of extra dimensions and the theoretical formalism used. In the context of the Randall--Sundrum model, a lower limit of 1.00 (2.06) TeV at 95% confidence level is set on the mass of the lightest graviton for couplings of k/Mpl = 0.01 (0.1). Combining with the ATLAS dilepton searches based on the 2011 data, the 95% confidence level limit on the Randall--Sundrum graviton mass is further tightened to 1.03 (2.23) TeV for k/Mpl = 0.01 (0.1).