A cooler/lunch bag has a detachable liner, which is attached to the bag by engaging a row of round studs on the bag with a row of “+” shaped slits in the liner. After the liner is detached, it can be folded up, inverted and covered by its plastic base in a storage position. Such cooler/lunch bag can be thoroughly cleaned and is suitable for long-term use, in contrast to the cooler/lunch bags with fixed liners, which become disposable when soiled.