Cristiano Ronaldo was the hero as Portugal beat an ultra-defensive Czech Republic 1-0 at the National Stadium here on Thursday in their quarter-final to qualify for the Euro 2012 semi-finals.

Ronaldo headed home a cross from Joao Moutinho 11 minutes from the end to set up a possible semi-final against either world champions Spain or France.

It was just reward after another starring performance from the Real Madrid man against opponents who failed to register a single shot on target and were hindered by the absence of injured playmaker Tomas Rosicky.

"We had the quality to pass into the semi-finals," said Ronaldo.

"We are happy but know the next match will be difficult but the team is very mature and we are ready.

"There are big smiles and good music all round us!"

Portuguese winger Nani, who also had an outstanding game, said that the victory while long in coming was deserved.

"We played really well, we were stylish on the pitch and it was a great team effort," said the Manchester United star.

"Now its going to be more difficult in each game but we are very confident.

"I had a couple of chances which went close but thats how it is in football, Ronaldo as well went close but he hit the target in the end."

As is so often the case in knock-out matches in big tournaments, the first half was a cagey affair.

Portugal struggled to string two passes together while centre-backs Pepe and Bruno Alves resorted to lumping long aimless balls up the field.

Czech Republic had some joy down their right with one particularly dangerous cross from Theodor Gebre Selassie only just being cut out by Pepe.

Moutinho hit a weak shot from 20 yards that Petr Cech gathered easily.

But then the Ronaldo show really took off.

The Real Madrid star sprung into life in the 25th minute as he darted across field, played a one-two with Nani, shrugged off Michal Kadlec and fired straight at Cech.

It was a rare burst of activity in an up-until-then tame affair but even that wouldn't have counted as referee Howard Webb penalised Ronaldo for pushing.

The 27-year-old was only just getting started, though.

On 33 minutes Pepe lobbed a ball into the box and Ronaldo sent an overhead bicycle kick wide of the upright.

Next up he sent a free-kick from almost 30 yards swerving wide but in stoppage time at the end of the half he demonstrated his full talent.

Raul Meireles knock a long ball into the box which Ronaldo controlled on his chest before turning Kadlec and prodding the ball past Cech, only to see it come back off the post.

It took Portugal only 20 seconds after the restart to show their intent as Meireles crossed for Hugo Almeida, a first half substitute for Helder Postiga, who seemed to have pulled a hamstring, but the Besiktas forwad headed over when it looked easier to hit the target.

Ronaldo then clipped the outside of the post with a free-kick from fully 30 yards.

Moutinho and Meireles combined to play Ronaldo in behind the defence as he came in off his left wing but his finish was skewed high and wide.

Porto's Moutinho had a crack from 20 yards on 64 minutes but Cech tipped it over the bar while Almeida sent another header woefully over.

Meireles cleverly played in Nani on 74 minutes but the winger's shot was deflected over the bar.

The goal Portugal's domination richly deserved finally came on 79 minutes as Moutinho made a determined run down the right and produced a peach of cross that Ronaldo headed home on the dive.

Full-back Joao Pereira had a chance to seal the match but he shot wide when well placed.