Objective Diagnostic of different dementia disorders is an important part of dementia care. So far, there is limited knowledge about how dementia is diagnosed in clinical routine, and there are few reports on the costs of the dementia work‐up leading to a diagnosis. Here, we examine the costs of diagnostic dementia work‐up in Sweden. Methods The analyses were made on the data from the Swedish Dementia Registry (SveDem) and included 11,561 dementia patients diagnosed during 2007–2010, mainly not only in specialist care (SC) (n = 53) but also some primary care centres (PC). We have studied differences in the use of investigations for dementia diagnostics such as cognitive tests, blood and cerebrospinal fluid analyses, radiological examinations and assessments of functions. Unit costs for each diagnostic investigation were combined with the use of these investigations for all cases in the database. Results are presented versus gender and stratified for age. Results The number of diagnostic tests performed was 2.8 in PC and 4.6 in SC. The average costs (€1 = SEK9 and US$1 = SEK7 in 2010) were SEK6777 in PC and SEK11,682 in SC. Age was the strongest cost predictor while there were no gender differences. There were also regional differences, ranging from SEK8231 to SEK14,734 in SC. Conclusions The SveDem database offers valuable information on the diagnostic procedures for dementia in daily clinical practice. The differences between PC and SC in diagnostic costs reflect national guidelines. The age effect needs to be studied more. Copyright © 2013 John Wiley & Sons, Ltd.