This study examines how and why investors change their information sources in valuation between book value and earnings after mergers and acquisitions (M&A) in both pre- and post-FAS 141(R) periods. We find that, in general, investors shift their information source from earnings to book value (especially the growth component) after M&A, and that such a shift is particularly strong after the adoption of FAS 141(R). We further find that FAS 141(R) improves the value relevance of book value components after M&A by looking at goodwill, other intangible assets and other balance sheet accounts that FAS 141 (R) amended.