Yes, if you're in a hurry or don't have dried lentils on hand, you can substitute the dried lentils with 2 or 3 15 ounce cans of pre-cooked lentils. The ratio of dried to canned lentils in this recipe would equal about 2.5 cans. I suggest rinsing the canned lentils before making your soup so they'll better absorb the flavors of your broth.