Spain's influential El Pais newspaper withdrew what it said was "false photo of Hugo Chavez" that it had published in its on-line and print editions on Thursday.
Venezuelan President Chavez has cancer and has been under medical treatment in Cuba where he underwent surgery in December. He has not been seen publicly for six weeks.
The grainy photo that El Pais originally splashed on its front page, billed as a global exclusive, portrayed the head of a man lying down with a breathing tube in his mouth.
El Pais, one of the biggest Spanish-language publications in the world and an institution both in Spain and in Latin America, said in a brief on-line statement that it had withdrawn the photo after ascertaining that the image was not of Chavez.
Venezuelan political opposition leaders have criticized government secrecy over Chavez's condition while his supporters have accused foreign media of being in league with the opposition to spread rumors that the president's medical condition is worse than it is.
"El Pais apologizes to its readers for the damage caused. The newspaper has opened an investigation to determine the circumstances of what happened and the errors that were committed in the verification of the photo," the newspaper said in the statement.
The photograph was on the paper's website for half an hour and also appeared in early editions of the print version of the paper, before the company stopped the presses and changed its front page, the company said.
(Editing by Jon Boyle)