Miksic was found guilty on Wednesday of damaging the honour and reputation of the president of the republic and his former opponent by claiming in the election campaign that the French secret service had bought Mesic a villa on the French Riviera.
At a 22 December 2004 news conference, Miksic labelled Mesic as a person unworthy of his duty and for which he was campaigning to be re-elected, said Judge Andrea Grahovac.
She said Miksic had crossed the line of permissible behaviour because honour and reputation were the highest moral values protected by the Constitution and must not be damaged even in an election campaign.
The judge said an aggravating circumstance was the fact that Miksic had slandered the president at a press conference and that his statement had been carried by all media.
Neither Mesic nor Miksic attended the sentencing. Miksic's attorney announced an appeal.
Mesic said earlier that in case he won the lawsuit against Miksic, he would donate the damages to a children's home.
Miksic was already given a two-month suspended sentence by the Municipal Court in Samobor for defaming Mesic last February.