take a look at the rear windows' glass at the back corner - where the epa emission rating is posted - if it reads "AT-PZEV" its the one with the smaller gas tank and no lean-burn

if it reads "ULEV" then its the regular version with the 13.2 gallon tank and lean-burn

if you check out honda's website on the civic hybrid and click the link for the full specifications, you will see that the emissions and epa mileage ratings are different for the two versions

From Honda's website: "*AT-PZEV vehicles are SULEV-rated with zero evaporative emissions and differ slightly due to emission standards. Available in California and some northeastern states."

hch specifications from honda - scroll down to emissions/mpg