As far as I understand the royal crown and royal title that some Polish rulers received were not heriditary till the 14th century (this was somehow universal for other central european states where also some rulers were kings and some weren't - how it exactly worked I don't really know). Now Boleslaw 'the brave' was awarded the crown for himself but after his son was overthrown the royal dignity was refused by the successors. Boleslaw 'the Bold' was never awarded the crown from outside but claimed it himself for Poland therefor challenging the imperial authority which was recognized superior by earlier dukes. His successors didn't dare doing so, especially with the strong Hohenstauffens in Germany I presume. Otoh maybe refused it also on grounds that acceptance of a royal crown from the German emperor meant a direct submission to his supremacy (like happened in Bohemia for example). I guess with the choice of either a crown and submission or a crown and war with the empire was one between bad and worseOriginally posted by szopen76
Actually POland _was_ kingdom, but it has no king. I could be wrong, but i guess since country had few times king, it was universally recognised as kingdom, even if currently there was none to pick the title.
Anyway, the formal title of the ruler in Krakow after 1138 was something of senior princeps iirc...
@Demetrios
For Silesia/Slask iirc there were after 1177 three formal duchies - Legnicko-Wroclawskie (Liegnitz/Breslau) ruled by Boleslaw Wysoki (the Tall), Raciborskie (Ratibor; later extended with Bytom/Beuthen and Oswiecim/Auschwitz) ruled by Mieszko Platonogi (Stumblefeet) and Opolskie (Oppeln) ruled by Jaroslaw, a son of Boleslaw. I presume this was still the case in 1187, Oppeln fell to Boleslaw again around 1201 (I presume after this son died heirless).