A solitary goal from Portugal's talismanic forward proved enough to give Paulo Bento's men a slim victory, despite both sides wasting their fair share of clear-cut chances.
The Seleccao skipper buried a fine finish after 36 minutes to give his side a narrow win, while Paulo Bento was able to shuffle his pack throughout the game as he looks for the most effective attacking formula.
After a slow start, Croatia was to create the first notable chance of the clash on six minutes. Ivica Olic failed to steer home an Ivo Ilicevic cut-back, with Eduardo left helpless between the posts.
From that point onwards, Ronaldo was to be the main catalyst of the half. The Real Madrid forward lit up proceedings on the pitch and ignited the atmosphere in Geneva with some driving runs, adding some excitement to an otherwise-sluggish first half. However, the 28-year-old spurned his first chance to break the deadlock on 18 minutes when he failed to connect properly with Fabio Coentrao's delivery.
Ronaldo wasn't to spurn another opportunity though, giving Portugal the game's opening goal on 36 minutes. After impressive work down the right from Silvio, the Deportivo defender's cross was set back to the captain by a fantastic touch from Silvestre Varela, and, after side-stepping the defenders, he made no mistake in slamming the ball left-footed into the bottom corner.
Croatia keeper Danijel Subasic was left similarly helpless merely five minutes later by the same man, as Ronaldo left the crossbar rattling. After nodding his header into the ground powerfully, the Portuguese goalscorer was dismayed to see his effort rebound off the woodwork, as Bento's men headed into the break with a slender lead.
Croatia made a strong start to the second half before Vieirinha carved out the next good opportunity. As the Wolfsburg man cut in towards the near post, Vierinha spotted Hugo Almeida unmarked at the back stick, but he found a Croatian shirt rather than the boot of his teammate.
On 78 minutes, Croatia then went close. After play was switched out to the right flank by substitute Alen Halilovic, the eventual cross lofted in search of Ivan Perisic narrowly escaped the winger, who nodded the ball just over Eduardo's bar. Perisic was then found again minutes later by a smart through-ball by Nikola Kalinic, but a poor first touch took the opportunity away from him.
Halilovic had the final clear opportunity of the game on 86 minutes, as the 16-year-old forced a smart save from Eduardo, who had to get down quickly to his right to palm the youngster's effort around the post.
Portugal went on to claim its second 1-0 win in as many games, but with both sides wasting a worrying amount of chances, the outcome of the game will perhaps leave question marks over the quality of both sides' strike forces heading back into World Cup qualifying matches.