I purchased this costume for my six-year-old grandson.  I was quite pleased with the quality; actually I was a little surprised at how well it was made.  I ordered a 7-8 for him and he is a small child anyway for six years of age.  It fit him perfectly, but I don't think it would fit an eight-year-old.  If in doubt, I'd order up a size.  He loves dressing up in it, but right now he loves anything that is GI Joe related.