We focus on automatic coreference resolution for blogs and news articles with user comments as part of a project on opinion mining. We aim to study the effect of the genre shift from edited structured newspaper text to unedited, unstructured blog data. We compare our coreference resolution system on three data sets: newspaper articles, mixed newspaper articles and reader comments, and blog data. As can be expected the performance of the automatic coreference resolution system drops drastically when tested on unedited text. We describe the characteristics of the different data sets and we examine the typical errors made by the resolution system.