Any mobile celeron above 2.0 GHz has 256K L2 cache. I am guessing they did this because going out to system memory more often requires more power than retrieving information from cache, thus shorting battery life. There is also an increase in performance.
Since the mobile Celeron has 256K L2, I would guess that it has similar performance to a Willamette, which also had 256K L2 cache.