Blood samples stored long-term in research studies could prove to be very valuable if it is possible to isolate good quality deoxyribonucleic acid (DNA) from them. The aim was to isolate and evaluate quality of DNA from 500 capillary blood samples, stored for 7 to 21 years in the DiPiS study. The samples were obtained from 5 different time-periods in the DiPiS study. DNA was isolated using QIAamp DNA Blood Mini Kit (Qiagen) and quantified using NanoQuant (Tecan). TapeStation (Agilent) was used to evaluate quality and fragmentation of n=100 DNA samples. It was found that it is possible to isolate good quality DNA from blood samples stored long-term, in the range of 7 to 21 years at -20 °C. There was significant difference in [260/280 nm] absorbance ratio between groups of samples stored for 7, 8, 12, 16 or 21 years and the quality control using n=100 samples revealed a significant difference in DNA integrity number (DIN) relative to storage time but not in fragment size. However, no correlation between sample quality and storage time could be found. The results suggest that good quality DNA can be isolated from the 7 to 21 years old blood samples in the DiPiS study and used in future analyses. The results from this study suggest that other studies that have blood samples stored long-term could isolate good quality DNA from these.