I bought my son (17 months and about 26lbs) a pair of the 2 piece Christmas Tree Pajamas sized 18-24. My little guy admittedly has a nice gut on him, but I think he's pretty average for his age. These jammies, while cute and made of awesome material are definitely snug on him. They're MEANT to be snug but, given he should be able to wear these for the next 6 months, I'd say they're a little too snug. Just something to think about before purchasing!