How to fix uneven walls?

We just remodeled our kitchen and when we went to put in the countertops we found out our walls are very uneven. The countertop lays flush on one side of the wall and on the otherside there is a gap 3/4in wide. What can we do to fix this.

Hi,

As long as the plaster is generally sound, cosmetically unattractive plaster walls can be "wallpapered" with strips of a canvas or fabric-like material. Historically, canvassing covered imperfections in the plaster and provided a stable base for decorative painting or wallpaper.

I have also heard that doing a spongepaint will often conceal the uneven walls. The texture will make it less noticeable.