Does changing WordPress Theme Affect My SEO?

[Pixelrage]

Only content and site structure will affect your site standing. Changing themes should not affect either, unless you are using a very sophisticated theme that changes the entire structure of your site (for instance, if you're switching from a magazine theme to a classified ads theme).

As long as the "directory tree" and flow of your site stay the same, as well as META titles, body content, number of on-page links, number of external links and number of internal links are all the same from one theme to the next, there should be no change (positive nor negative) by switching themes.