Competition and data protection law are two powerful regimes simultaneously shaping the use of digital information, which has given rise to new interactions between these areas of law. While most views on this intersection emphasize that competition and data protection law must work together, nascent developments indicate that these legal regimes may sometimes conflict.  In the first place, firms faced with antitrust allegations are to an increasing extent invoking the need to protect the privacy of their users to justify their impugned conduct. Here, the conduct could either be prohibited by competition law despite of data protection or justified under competition law because of data protection. In the EU, no such justification attempt has reached court-stage, and it remains unclear how an enforcer ought to deal with such a claim. In the second place, competition law can mandate a firm to provide access to commercially valuable personal data to its rivals under a competition law remedy. Where that is the case, the question arising in this connection is whether an enforcer can and should design the remedy in a way that aligns with data protection law. If so, the issue remains of how that ought to be done. The task of the thesis has been to explore these issues, legally, economically, and coherently.  The thesis has rendered four main conclusions. First, data protection has a justified role in EU competition law in two ways. On the one hand, enhanced data protection can increase the quality of a service and may thus be factored in the competitive analysis as a dimension of quality. On the other, data protection as a human right must be guaranteed in the application of competition law. Second, these perspectives can be squared with the criteria for justifying competition breaches, in that data protection can be invoked to exculpate a firm from antitrust allegations. Third, in that context, the human rights dimension of data protection may entail that the enforcer must consider data protection even if it is not invoked. However, allowing data protection interests to override competition law in this manner is relatively inefficient as it may lead to less innovation, higher costs, and lower revenues. Fourth, the profound importance of data protection in the EU necessarily means that enforcers should accommodate data protection interests in designing competition law remedies which mandate access to personal data. This may be done in several ways, including requirements to anonymize data before providing access, or to oblige the firm to be compliant with data protection law in the process of providing access. The analysis largely confirms that anonymization is the preferable option.