Necid opened the scoring after 12 minutes and the game was as good as safe just before the half-hour mark when Kadlec fired home from just outside the area. Midfielder Tomas Rosicky claimed the assist for both goals but his creative influence was hardly required thereafter as the visitors eased to a win that helped build on their 1-0 success over Scotland on Friday night.
The win moved Czech Republic up to second in Group I with six points from three games. While their early goals decided the contest they masked an otherwise uncomfortable opening ten minutes for the visitors as they twice narrowly avoided going behind to the minnows.
Liechtenstein midfielder Sandro Wieser was ruing his finishing when he headed over from six yards before the woodwork kept out Michael Stocklasa's header. Just minutes later, however, they were behind. Necid profited fully on Rosicky's clever run and pass to thrash a sweet strike in from just outside the area.
The Arsenal midfielder's creativity was proving too much for the home team and he set up the second after 28 minutes with a run down the left before threading a pass to Kadlec who powered in a low strike from the edge of the area.
Czech Republic were now in control and a third before the break narrowly eluded them when Zdenek Pospech shot wide after Kadlec's cross found him 12 yards from goal.
It proved to be the last of the action as a ludicrously mundane second period wound down without much action. Substitute Roman Bednar had the best chance for a third goal but he saw a 20-yard shot parried by Peter Jehle before shooting wide when better placed.