Hi Tina, both sentences are perfectly correct. Spanish is a rich language with many tenses and each of them offers different nuances. The difference between the two sentences is: ♦ In the first one there is uncertainty we even propose to him to come. ♦ While in the second one assumes that he's going to be invited or he's already been invited to this party. Although there is still uncertainty that he will come. 1. Dudo que Juan viniera a la fiesta → I doubt that John came to the party. ☛ In the hypothetical case that we or someone would offer to him. 2. Dudo que Juan venga a la fiesta → I doubt that John comes to the party -in the future-) ☛ If we or someone offer it, or even if we've already proposed it to him. I really hope this helps you, Tina. Kindest regards.

Both are correct. Fernando explanation is perfect. But i want to add another use of: "dudo que Juan viniera a la fiesta". We use this construction to speak about party in the past.. when we don't know if finally Juan came or not...

"Dudo", va en presente de indicativo, y "Venga"en presente de subjuntivo. Esa es la correcta. "Viniera", imperfecto de subjuntivo, se usa con tiempos del pasado o condicional.

I think the second one is correct, because you're doubting about if Juan is gonna go to the party. If you want to use "viniera" you should use "ojalá" (that means "I hope") instead of "dudo": Ojalá Juan viniera a la fiesta. That means you think he won't come at the party at all as you said :)

la primera suena muy rara. para mi solo la segunda es correcta. and means that you don't think he is going to come