Communication is typically understood in terms of what is communicated. However, the importance of what is intentionally or unintentionally left out from the communication process is high in many fields, notably in communication about environmental and health risks. The question is not only about the absolute lack of information. The rapidly increasing amount and variability of available data require actors to identify, collect, and interpret relevant information and screen out irrelevant or misleading messages that may lead to unjustified scares or hopes and other unwanted consequences. The ideal of balanced, integrative, and careful risk communication can only rarely be seen in real-life risk communication, shaped by competition and interaction between actors emphasizing some risks, downplaying others, and leaving many kinds of information aside, as well as by personal factors such as emotions and values, prompting different types of responses. Consequently, risk communication is strongly influenced by the characteristics of the risks themselves, the kinds of knowledge on them and related uncertainties, and the psychological and sociocultural factors shaping the cognitive and emotive responses of those engaged in communication. The physical, economic, and cultural contexts also play a large role. The various roles and factors of absent information in integrative environmental and health risk communication are illustrated by two examples. First, health and environmental risks from chemicals represent an intensively studied and widely debated field that involves many types of absent information, ranging from purposeful nondisclosure aimed to guarantee public safety or commercial interests to genuinely unknown risks caused by long-term and cumulative effects of multiple chemicals. Second, light pollution represents an emerging environmental and health issue that has gained only limited public attention even though it is associated with a radical global environmental change that is very easy to observe. In both cases, integrative communication essentially involves a multidimensional comparison of risks, including the uncertainties and benefits associated with them, and the options available to reduce or avoid them. Public debate and reflection on the adequacy of risk information and on the needs and opportunities to gain and apply relevant information is a key issue of risk management. The notion of absent information underlines that even the most widely debated risk issues may fall into oblivion and re-emerge in an altered form or under different framings. A typology of types of absent information based on frameworks of risk communication can help one recognize its reasons, implications, and remediation.