I think, they actually have exactly same meaning but it's used slightly different. if you say 배고프면 라면 먹어.(If you are hungry, eat the instant noodle.) 배고프다면 라면 먹어. (If you are hungry, eat the instant noodle.) the second one is a bit awkward but it depends on. 배고프면 라면 먹어; it sounds like "If you are hungry, eat the instant noodle" 배고프다면 라면 먹어; it's actually same meaning but it sounds more like "If you are hungry, eat the instant noodle but if you are not, don't eat or you don't need to eat." 내 미래의 여자친구가 예쁘면 좋겠다. 내 미래의 여자친구가 예쁘다면 좋겠다. in this case, 예쁘면 좋겠다. sounds more like "I want a pretty girlfriend" and 예쁘다면 좋겠다. sounds more like "If my future girlfriend is pretty it would be nice." ~다면 sounds more strong as a specific condition than ~면 but but in many situation you can use both of them as a same meaning as well.