Howe calls PSG game 'the defining moment' in Newcastle's season
Newcastle stunned PSG 4-1 in the first meeting at St James' Park but have slid from top to bottom in the standings after successive defeats to Borussia Dortmund and would be unable to reach the last 16 if they lose to PSG.
"This is the defining moment of our Champions League campaign and we'll give everything," Howe told a pre-match press conference in Paris on Monday.
"It's difficult to talk about Paris' players. They have quality everywhere," he said.
"They've been scoring goals for fun. But our structure and resilience has been good, and we're going to need to be as good as we know we can be."
Howe's side have been boosted by a Premier League win over Chelsea at the weekend.
"The mood of the group is good," he said.
"It was a pivotal moment (the Chelsea win) - it would have been very easy to feel sorry for ourselves.
"The lads did well to play at such a high level. But we are not in the position we want to be in in the Champions League, and it is imperative we do not lose tomorrow."
PSG are second, a point behind leaders Borussia Dortmund in a tight Group F, with AC Milan and Newcastle also targeting the knockout rounds with just three points separating the four teams.
"We were ruthless against Paris in the first game, and we don't want any excuses this time," Newcastle goalkeeper Nick Pope said.
"It's a tough game but a good challenge. We've spoken as a group about what we'd have given to be here when we were chasing Champions League football."
PSG coach Luis Enrique said his team were "far" from meeting his expectations and had "a lot of room for improvement" but he was convinced they could use their home advantage.
"The Parc des Princes is a cauldron which lifts us," said the Spaniard.
"Newcastle know how to exert pressure very well, they need a victory because they are bottom of the group.
"If you watch Newcastle's game against Chelsea, their physicality is important.
"They went to press with up to six players and they are capable of maintaining a very quick pace. I expect that same intensity against us, but we will be prepared."
