Today I have found this and the problem is gone. I've pasted an appropriate piece of amaroK's FAQ below:
amaroK is not using the tags I know are in my files!
If Konqueror or other apps are displaying different Title, Artist, Album or Genre information than amaroK is picking up when it creates your collection, it may be reading the older ID3v1 format tags rather than the newer ID3v2 tags. This can be due to your Encodings setting:
- Go to Settings, Configure amaroK, and then find the Encodings section of the Settings panel. Unclick all checkboxes to "Do not decode the following as latin1".
- Rescan your collection to pick up the ID3v2 tags.