Carlo Ancelotti's men took command at the Mestalla with first-half goals from Argentinian pair Ezequiel Lavezzi and Javier Pastore, although Valencia were handed a late lifeline with Adil Rami's strike.
PSG also saw star striker Zlatan Ibrahimovic sent off in the dying seconds and the Sweden international will now miss the return match in Paris in two weeks.
However, Valverde is aware their opponents are still favourites to progress to the quarter-finals, even without their leading scorer.
"We have to recognise they are a great team with great players and they showed their strength," he said in quotes on Marca.
"Eventually we managed to score a goal and that gives us some hope, but we know the return match will be very difficult.
"There are no buts. They are very strong and every counter-attack is very dangerous. In all honesty, we were probably too naive in the first half.
"We must be aware they have outstanding players like Lucas Moura and Lavezzi. Ibrahimovic's red card will not really help us as they have many resources in their squad.
"It will be complicated in Paris but it is a match, we will go there to play and we have to try."
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