Cyprus recorded a shock 4-4 draw in Portugal in September 2010 but since then new coach Paulo Bento has replaced the sacked Carlos Queiroz and revived the team's fortunes.
"We are much improved but we cannot take it easy and make the same mistakes we did in the first game. Our goal has to be to keep top spot," Ronaldo told Portuguese television.
"We cannot look upon Cyprus as a weaker team. They stole two points from us," added the world's most expensive player.
Portugal have scored seven goals in the last three qualifiers to give Bento a perfect 100 percent record with three wins. They are top on goal difference, level with Norway and Denmark on 10 points.
Portugal's preparations suffered a setback on Wednesday when central defender Ricardo Carvalho, who has played at two European championships and two World Cups, quit the team camp, saying he had been "disrespected."
"I feel in full physical and mental form, as I have shown for my club and country, but if I am made to feel unnecessary and am not told so, then the only way is out," Carvalho said in a statement carried by state news agency Lusa.
"Having earned 75 caps and been deeply dedicated in defending the national side's reputation, I have never before felt so disrespected and wounded in my dignity," added the 33-year-old Real Madrid player.
Ronaldo has started this season on fire for Real Madrid, netting at the Nou Camp against Barcelona in the Spanish Super Cup and then grabbing a hat-trick against Real Zaragoza on the opening day of La Liga.
Fellow winger Nani is also on form, having scored in Manchester United's 8-2 rout of Arsenal at the weekend.
Raul Meireles is a doubt after injuring his collarbone playing for Liverpool but centre-back Pepe is ready to deputise as holding midfielder, as he often did under Queiroz.
Real defender Ricardo Carvalho skipped the last training session in Portugal without offering Bento an explanation. He did not fly to Nicosia with the squad and it is not yet clear whether he will travel later.
Sporting's Rui Patricio is set to take over in goal from Eduardo, who has been mainly on the bench at his new club Benfica.
Cyprus coach Nicos Nioplias will face a tough test in his first competitive match after replacing Greek compatriot Angelos Anastasiadis who was sacked in April after a poor run.
Cyprus are fourth with two points from four matches.
"Portugal will be a hard job for us. Our aim is to not let them win and to achieve that we have to be focused and avoid making mistakes," said Nioplias.
Probable teams:
Portugal: Rui Patricio; Joao Pereira, Rolando, Bruno Alves, Fabio Coentrao; Pepe, Joao Moutinho, Ruben Micael; Cristiano Ronaldo, Helder Postiga, Nani.
Cyprus: Antonis Giorgallides; Savvas Poursaitides, Sinisa Dobrasinovic, Georgos Merkis, Athos Solomou; Andreas Stavrou, Constantinos Charalambides, Andreas Avraam, George Efrem, Koullis Pavlou; Yiannis Okk
