In most cases Quand and Lorsque are interchangeable and they both mean When, but sometimes they differ in meaning: - Quand & Lorsque - temporal correlation (Lorsque is just more formal): Je marchais lorsque/quand tu m'as téléphoné (I was walking when you called me) Lorsque je t'ai vu, j'avais peur (When I saw you, I was afraid) - Quand - repeated correlation (meaning "chaque fois que"): Quand il est là, elle ne parle pas. (Whenever he is there, she doesn't speak) - Quand - interrogative adverb: Quand vient il me voir? - Lorsque means "whereas" too: J'ai crié lorsqu'il a fallu courir (I screamed when (whereas) I should have run) I hope this helps. Bye!