handmade-candles is read as handmade, candles and handmade candles handmade_candles is read as handmade_candles Hyphens are treated as a separator. Underscores are not. Try an "allinurl" search for a quoted or unquoted two word phrase and show me just how many results have an underscore. allinurl:"handmade candles" allinurl:handmade candles Use hyphens. The reason you are seeing more underscores is unrelated to the use of underscores. Those pages rank for other factors, as they should.