  We present a search for extra dimensions in the diphoton channel using the
CMS detector at the Large Hadron Collider. The search is focused on the
forthcoming 2009--2010 run at 10 TeV center$-$of$-$mass energy and $\sim 100$
pb$^{-1}$ of data. We discuss event selection and optimization, as well as
data-driven methods of estimating various backgrounds and efficiencies. The
dominant source of background after all the selection requirements is SM
diphoton production. We quote the sensitivity of the search both in terms of
limits on the parameters of large and warped extra dimensions in the case of no
excess observed, and in terms of signal discovery significance, if an excess is
seen in data.
