Hi, There is no rules about it : this is more a question of sonority than a real grammar problem. You can use them both, but for some phrases one will be heavy, or make the phrase sound weird. But that would be grammatically correct anyway. Best regards, Chris

Okay with Chris Aussitôt que maybe a bit sooner.....than des que We dont use much lorsque as in a sentence "lorsque il" really sounds crap... better go "des qu'il"

Bonjour, "Lorsque" is used in literature and not much in spoken language ...

for me there are no rule, you can use both in the same case