  We introduce a model which uses semi-analytic techniques to trace formation
and evolution of galaxy disks in their cosmological context. For the first time
we model the growth of gas and stellar disks separately. In contrast to
previous work we follow in detail the angular momentum accumulation history
through the gas cooling, merging and star formation processes. Our model
successfully reproduces the stellar mass--radius distribution and
gas-to-stellar disk size ratio distribution observed locally. We also
investigate the dependence of clustering on galaxy size and find qualitative
agreement with observation. There is still some discrepancy at small scale for
less massive galaxies, indicating that our treatment of satellite galaxies
needs to be improved.
