In a systematic search over 11 cluster fields from Cluster Lensing And Supernova survey with Hubble ( CLASH ) we identify ten passively evolving massive galaxies at redshift z \sim 2 .
We derive the stellar properties of these galaxies using HST WFC3/ACS multiband data , together with Spitzer IRAC observations .
We also deduce the optical rest-frame effective radius of these high redshift objects .
The derived stellar masses and measured effective radii have been corrected by the lensing magnification factors , which are estimated by simply adopting the spherical NFW model for the foreground cluster lens .
The observed near-IR images , obtained by HST WFC3 camera with high spatial resolution and lensed by the foreground clusters , enable us to study the structures of such systems .
Nine out of ten galaxies have on average three times smaller effective radius than local ETGs of similar stellar masses , in agreement with previous works at redshift 1.5 < z < 2.5 .
Combined with literature data for z \sim 2 , we find that the mass-normalized effective radius scales with redshift as r _ { e } / M _ { \star } ^ { 0.56 } \propto ( 1 + z ) ^ { -1.13 } .
We confirm that their size distribution shows a large scatter : from normal size to \sim 5 times smaller compared to local ETGs with similar stellar masses .
The 1- \sigma scatter \sigma _ { { log } r _ { e } } of the size distribution is 0.22 and 0.34 at z \sim 1.6 and z \sim 2.1 , respectively.The observed large size scatter has to be carefully taken into account in galaxy evolution model predictions .