presto means soon, fast, quickly, early (早く - まもなく) subito means immediately, quickly (すぐ) examples: il treno arriverà presto the train will arrive soon questa mattina mi sono svegliato presto this morning I woke up early fai presto! do it quickly lo voglio subito! I want it right now torno subito I will be back soon When you mean "quickly" you can use both: faccio presto / faccio subito I do it quickly (in a short while) Be careful because "subito" is also the past participle of "subire" (suffer, endure, undergo) sometimes we use the accent to make difference between subito adverb and subito past participle: sùbito -> adverb subìto -> past participle ho subito un torto (past participle of subire) 不当な扱いを受けました (I hope that I translated in the right way ^^)

subito means immedaiatly, without waiting. presto means soon,