Yes, I am pretty sure that I need to keep the blackish fills (i.e. they are not just overlapping strokes). I was, however, able to select all paths containing pure white fills with find tool. Thank you for mentioning that, it seems quite useful. However, it would be too complicated to search for all...

Thank you both for your answers. I am sorry that I didn't make myself clear in my first post. I also have problems with selection. I didn't realize it is that simple to remove a fill color and to set a stroke color. Setting of the stroke color for all objects works perfectly as you suggested, becaus...

I have an (apparently) black and white eps image with many small paths which are often interlaced with each other. Some of them are closed and filled with white color while some of them are open. It is also possible that some of the closed paths are filled with a color very similar to white, but not...