"The semi-final is going to be really tough. Winning away in the Heineken Cup knockout stages doesn't happen all that often. Even take a look at Toulouse in their quarter-final, they were favourites, but they were away from home and couldn't win," said Schmidt who could face his old club Clermont in the semis.
"Cardiff came into this game at the end of a really tough week for them, and we know the semi is going to be totally different and much, much tougher.
"And you know the hard thing about the Heineken Cup is that you can't really take any momentum into a game. The Pro12 is obviously a different level so whether it's Saracens or Clermont it's going to be difficult.
"If we go to Bordeaux, Clermont are going to have to travel a bit as well as us. It's a pretty foreign field for them. We realise that being at home last season in the semi was a massive advantage for us, and perhaps if we'd played Toulouse in France it would've been a different result.
"You earn your quarter-final from your pool performances and where you end up after that is largely down to luck, but then that's part of the mystique of the Heineken Cup. Whether we have to go Twickenham or Bordeaux, we know that the Leinster supporters will be trying to make it as near as possible a home game for us.
Despite scoring four tries and at times playing with the sort of flair which makes his team favourites in many pundits' opinion to become only the second club to win back-to-back Heineken Cup titles, Schmidt accepted that the level of performance dropped away after the interval.
"Our performance did relax a bit in the second half, but what was really pleasing was the way we defended our line. It brought me back to the Bath game in Round 4 when we scored some great tries, but we conceded a few as well, so this time we dug in and kept our line intact.
"It's always nice to score those sort of tries, but there were other areas of execution which wasn't as accurate. For me the line-out needed to be a bit better, and a couple of times I thought we forced passes when we had Cardiff going backwards and probably in those last 10 minutes I think we should have got one more score. "