Insomnia is a major public health problem. In addition, insomnia is strongly associated with other somatic and mental health problems as well as with an increased mortality rate. Treatment of insomnia is highly desirable, mostly to decrease the burden of insomnia itself. But it might also contribute to a decrease of the associated somatic and mental health problems such as depression and cardiovascular risk. The overall effects for insomnia treatments seem to be in line with psychological treatments for other disorders such as depression, social phobia, panic disorder with or without agoraphobia. However, the magnitude of the effects varied between the different outcome parameters. Despite the limitations we conclude that CBTI, either its components or the full package, is effective in the treatment of insomnia.