The aim of this paper is to present the result of an attempt of functional analysis of the Polish translation of Tove Jansson's biography: Tove Jansson. Ord, bild, liv written by Boel Westin. The comparative analysis of the text is based on the Margaret Amman's five step functional model of quality assessment with incentive in the translated text not the original. The quality criteria for analysis follow the conclusions of professor Andrzej Kopczyński postulating the application of a unique combination of cultural, situational and language factors in every analysis. The analysis itself follow the guide-lines of language correctness described by professor Andrzej Markowski. The results of analysis revealed different types of internal lingual - systemic and internal lingual - stylistic mistakes proving the point that the Polish text of translation do not meet qualitative criteria set for a good translation.