The Real Madrid forward has been picked out as the main danger in Germany's first group fixture, but Lahm says Germany know how to take care of him and will not be focusing on just one opponent.
"Ronaldo is one of the best players in the world," said the Bayern Munich full-back.
"He has great pace, dribbles at you quickly, and he has a good finish with both legs and his head.
"He is a complete player and we have got to defend him as a team. You cannot go one on one against Ronaldo."
"Ronaldo is a sensational player so it is right to talk about him, but the team is focusing on their whole team and not just Cristiano Ronaldo."
Lahm will be relieved of much of the responsibility of dealing with Portugal's dangerman after confirming he will be playing wide left throughout Euro 2012.
The Bayern full-back started his career on the right-hand side of the defence, but was soon moved on to the left after a two-year loan spell with Stuttgart.
He has spent much of his time with Bayern on the left before shifting back across to the right under Jupp Heynckes last season.
Germany coach Joachim Low has now decided his captain will be restored to the position he has filled almost exclusively since gaining his first Germany cap in 2004.
"It has been decided that I will play left," said Lahm during a press conference at Germany's base in Gdansk.
"I have discussed it with the coach and he sees me better on the left."
That leaves the question over who will get to deal with Ronaldo, and the likely candidate Jerome Boateng no longer looks favourite.
The Bayern defender has upset the German Football Association with his behaviour last weekend when he was spotted out partying into the early hours the night before flying out to Poland with the national team.
"He has a debt to pay," said Low. "I am not happy with what he did at the weekend and I have spoken to him about it."
Low also revealed his alternative for the right-back berth, saying that Borussia Dortmund midfielder Lars Bender has impressed him in training.
"Lars Bender can play well there so we will wait until tomorrow before making decisions, I will take my time," said Low.
"All I will say is that I am pleased with what I have seen of Lars Bender playing on the right.
"Before the preparation started, I said I could imagine a few players in different positions and Lars is a player who could play at full-back, even though he never played there for his club.
"All he has to learn is when to go forward and when to stay back. Nobody can do that as well as Philipp Lahm, but Bender has great potential and I can see some incredibly good things with him."
Low has also seen improvements in the condition of injury concerns Per Mertesacker, Miroslav Klose and Bastian Schweinsteiger in recent days, and all three should be available for selection on Saturday, confirmed the Germany coach.