Subjective cognitive impairment is a condition with an increased risk of conversion to primary neurodegenerative dementias, especially to Alzheimer's disease. Therefore, persons with this disorder require clinical evaluation and continuous monitoring. They report subjective decline in cognitive functioning which cannot be objectively confirmed. Different pathological conditions may present with subjective cognitive problems. Often it is associated with mild forms of depression. By revealing underlying etiology, it is possible to estimate potential of progression and outcome of cognitive impairment. Several imaging and neurobiochemical biomarkers enable detection of underlying Alzheimer's disease pathology in persons with subjective cognitive impairment. Causal or disease-modifying therapy for Alzheimer's disease is still missing. Since it would be the best to start this treatment in the earliest, preclinical stage of disease, identifying persons with subjective cognitive impairment with underlying Alzheimer's disease will become extremely important.