Transiting planets are essential to study the structure and evolution of extra-solar planets .
For that purpose , it is important to measure precisely the radius of these planets .
Here we report new high-accuracy photometry of the transits of OGLE-TR-10 and OGLE-TR-56 with VLT/FORS1 .
One transit of each object was covered in Bessel V and R filters , and treated with the deconvolution-based photometry algorithm DECPHOT , to ensure accurate millimagnitude light curves .
Together with earlier spectroscopic measurements , the data imply a radius of 1.22 ^ { +0.12 } _ { -0.07 } R _ { J } for OGLE-TR-10 b and 1.30 \pm 0.05 R _ { J } for OGLE-TR-56 b .
A re-analysis of the original OGLE photometry resolves an earlier discrepancy about the radius of OGLE-TR-10 .
The transit of OGLE-TR-56 is almost grazing , so that small systematics in the photometry can cause large changes in the derived radius .
Our study confirms both planets as inflated hot Jupiters , with large radii comparable to that of HD 209458 b and at least two other recently discovered transiting gas giants .