Viral respiratory infections are one of the leading causes of morbidity and mortality, especially in children, elderly and immunocompromised patients. The inclusion of post-mortem studies to diagnose the infection causing mortality could be beneficial in specifying new pathogens and determining strategies for treatment and prevention. The aim of this study was to research viral etiology by applying multiplex real-time polymerase chain reaction (Rt-PCR) method in autopsy cases who have been considered to have a respiratory infection and to assess whether the viruses detected are the primary cause of the infection and whether they have any contributory effect on the mortality together with histopathological evidence. In this study, we included a total of 834 cases consisting of sudden death cases from infantile-pediatric age group and autopsy cases from > 18 year age group with suspected respiratory tract infection in our laboratory between January 2013 and May 2017. Of 834 cases, 468 (56.1%) were male and 366 (43.9%) were female, there were 191 (22.9%) cases between 0-1 months, 593 (71.1%) cases between 1 month-18 years, and 50 (6%) cases in the > 18 years age group. In 728 of 834 (87.3%) cases nasopharyngeal/tracheal swab samples and in 106 (12.7%) of them paraffin-embedded lung tissue samples were studied by the use of "FTD Respiratory 21 (Fast-Tract Diagnostics Luxemburg)" kit, with multiplex Rt-PCR method. The post-mortem samples were evaluated for human rhinovirus (HRV), parainfluenza viruses (PIV) (1, 2, 3, 4), influenza virus type A and B (INF-A, INF-B), enterovirus (EV), human bocavirus (HBoV), adenovirus (AdV), human coronavirus (HCoV 229,63,HKU,43), human metapneumovirus A ve B (HMPV-A/B), parechovirus, respiratory syncytial virus (RSV A/B) and Mycoplasma pneumoniae. In our study, at least one respiratory virus was detected by Rt-PCR in 379 (45.4%) of total 834 cases, whereas no viral agent was identified in 455 (54.6%) of the cases. One viral agent was detected in 278 (33.3%), two viral agents were detected in 83 (9.94%) and three viral agents were detected in 18 (2.16%) cases. Overall, the most common viral agent was HRV 110 (13.2%) followed by AdV 39 (4.7%) and RSV A/B 33 (4%). In pediatric cases the rate of positive results for respiratory viruses was 31.8% and in adult group it was 20% (p= 0.032). The most common virus detected among children was HRV and INF-A in adult group. In 101 (12.1%) cases infections caused by two or three agents were diagnosed. Infections with two causative agents were detected as 2.6% (5/191) in 0-1 month age group, 13% (77/593) in 1 month-18 year age group and 2% (1/50) in > 18 age group. The most frequently observed co-infections with double causative agents were HRV and INF-B, HRV and PIV, HRV and HBoV, HRV and AdV combinations. Infections with three causative agents were detected completely among 1 month-18 year age [3% (18/593)] group. In our study, 318 (38.1%) cases had no signs of infection in the postmortem histopathological examination of the lung tissues, while the most common finding was lobular pneumonia/purulent bronchitis in 233 (28%) cases and the second was interstitial pneumonia in 168 (20.1%) cases. When all cases were evaluated in terms of infection, positive results were detected in 469 (56.2%) cases. As a result; postmortem microbiological diagnosis with autopsy and histopathological detection of the patients who are thought to have respiratory tract infection will also determine the infectious agents causing death.