We describe four channels through which breakups can potentially increase idiosyncratic volatility for parent firms. These are: loss of diversification (portfolio effect), change in growth opportunities, change in operational efficiency, and the flow and assimilation of information (information effect). The relevance of each channel depends on the mode of a breakup. We explain conceptually and show empirically, using a sample of 530 breakups (259 spinoffs and 271 equity carveouts), that the portfolio effect is dominant for spinoff parents, while the information effect gains importance for carveout parents. Our novel insight is that the magnitude of the information effect depends on the pre-announcement information set held by investors; we provide a simple state-space model and empirical evidence to support this intuition. We also find a relation between the change in operational efficiency and the change in idiosyncratic volatility for spinoff parents.