Objective: To investigate long-term symptoms after acute COVID-19, the link between symptoms and respiratory function, radiological changes in the post-COVID period, and risk factors for post-COVID syndrome. Methods: In this cross-sectional study, 123 participants who were admitted within the first 3 months were categorized as group 1, and those who applied after 3 months were categorized as group 2. According to thoracic imaging and pulmonary function tests, patients were split into 3 groups as mild, moderate and severe. Results: At least one symptom was present in 91.9% and 61.8% in acute and post-COVID period, respectively. Pulmonary function tests were normal in 60 (70.6%) in the first three months, and 30 (78.9%) in 91-days to 1-year period after acute COVID-19 infection. After 3 months, 22.4% of chest X-rays and 7.9% of computerized tomography revealed progression. Patients who developed acute complications (OR 9.91, 95% Cl 1.93-50.87), had 2 or more symptoms at admission (OR 7.73, 95% CI 2.56-23.33), had 1% to 14% CT involvement (OR 3.05, 95% CI 1.06-8.79), or had 50% or more CT involvement (OR 14.68, 95% CI 1.24-172.55) had a higher risk of developing post-COVID syndrome. Conclusions: COVID-19 symptoms can last for long time. Severity of symptoms, acute complications, and the extent of radiological involvement may all contribute to elevated risk of post-COVID syndrome. As a result, patients with COVID-19 should be checked for long-term clinical difficulties on regular basis.