ENThe article refers to the Biržai Radziwiłłs’ operations for obtaining favourable verdicts in property trials against other Crown and Lithuanian magnates thanks to gaining favour of tribunal deputies. The author decided to discuss deputy elections within the framework of all the preparations for tribunal trial, because their discussing without overt and covert actions preceding the election of deputies does not allow us to appreciate the significance and specificity of deputy sejmiks in relation to electing members of the parliament (Sejm). The main thesis of the article is the statement that for the magnates and the nobility the Tribunal was of equal importance to the Sejm, and deputy elections enjoyed equal, if not bigger, interest, than the elections of members of the parliament, because the tribunal judges decided cases concerning both the magnates and the whole nobility, and not only the representatives of local elites aspiring to a political career. Keywords: magnates, the Radziwiłłs, deputy sejmiks, tribunal campaign.