**Holders Chelsea reached the FA Cup quarter-finals after with a 4-1 victory after Cardiff had briefly threatened to cause a massive shock.Didier Drogba put Chelsea in front in the second minute but Michael Chopra stunned the home side with an equaliser before half-time.
But second-half goals from Michael Ballack, Daniel Sturridge and substitute Salomon Kalou put Carlo Ancelotti's side into the last eight.
Michael Ballack goal that is the inspiration for the blue forces continue to attack the opponent without fatigue, until finally created 2 goals again
Chelsea got off to a great start when John Obi Mikel's long ball put Drogba in the clear and the Ivory Coast striker ran on to fire past the static David Marshall.
It was Drogba's fourth goal in three games since his return from the African Nations Cup and his 23rd of the season.
Cardiff almost equalised when Peter Whittingham's free-kick was sent towards the top corner by Anthony Gerrard.But with City ready to celebrate an equaliser, Hilario somehow managed to get across and tip the ball over the bar.
In the 25th minute, Drogba was unlucky with an overhead kick from six yards when a cross from Michael Ballack had found him ahead of his marker.
Fortunately for Marshall in the City goal, Drogba's effort went straight to him.Chelsea remained in control of the game with Cardiff restricted to rare counter-attacks.But one of them paid off in stunning fashion in the 34th minute when they equalised through Chopra.
The Cardiff striker shocked the home side with his 17th goal of the season.Chopra got clear of Alex to head Chris Burke's cross into the net beyond the helpless Hilario, to the delight of the 6,000 travelling City fans.The Cardiff equaliser had certainly livened the game up but Chelsea gradually managed to get on top once more.
Sturridge, who has scored in the last two rounds, was a yard wide with a 25-yard shot in the 43rd minute.Chelsea's passing began to go astray as the half wore on and Cardiff were able to end the first half on level terms.
Chelsea replaced the ineffective Joe Cole with Kalou at half-time.
Drogba, the only Chelsea player really on his game, found Marshall alert when he tried to send a 25-yard free-kick inside the near post just seconds after the restart.
But Chelsea were back in front in the 51st minute when Drogba's pass evaded Mark Kennedy to put Michael Ballack through on goal. The Germany captain kept his cool to volley the ball over Marshall and make it 2-1.
Chelsea defender Alex was unlucky to see a header cleared by the Cardiff rearguard on the hour as the home side pressed for a third goal.
The home side were again in control with Drogba at the heart of all their best moves.The Ivory Coast striker was unlucky not to get on the end of a through-ball from Paulo Ferreira while Sturridge shot well wide from 20 yards in the 67th minute.
Chelsea finally got a third in the 69th minute when a scrappy build-up allowed the ball to run loose to Sturridge, who slipped it beyond Marshall.
It was his fourth goal in the competition - and his last contribution before being replaced by Florent Malouda.
Cardiff continued to make sporadic forays into the Chelsea half and on one such attack, Kevin McNaughton was a yard wide with a 20-yard angled drive.
Whittingham then brought a fine save out of Hilario with a low drive from 25 yards as Chelsea rested on their two-goal lead.
However, Kalou made it 4-1 in the 86th minute when he superbly headed home a cross from Ferreira.The Ivory Coast striker twisted his body in mid-air to send the header over Marshall's reach and into the top corner of the net.
Malouda was way off target in the 90th minute when he tried his luck from the edge of the penalty area - but Chelsea had done enough to go through to the last eight.
Cardiff : Marshall, McNaughton, Gyepes, Gerrard, Kennedy, Rae (Blake 74), Whittingham, Burke (McCormack 78), Wildig (Taiwo 90), Chopra, Bothroyd
Chelsea :Hilario, Carvalho, Ferreira, Alex, Lampard, J Cole (Kalou 46), Mikel, Ballack, Zhirkov, Drogba (Borini 88), Sturridge (Malouda 78)