The new coronavirus infection caused by the SARS-CoV-2 virus has become a real challenge for the world’s population. Despite the fact that vaccines have been developed and the effectiveness of antiviral drugs has been demonstrated, COVID-19 continues to be an urgent problem. SARS-CoV-2 is genetically modified due to the accumulation of mutations, new strains with high virulence appear that distort the immune response. In addition, it has been shown that the virus can persist in the body for a long time, which ensures the maintenance of an inflammatory response and causes the persistence and recurrence of symptoms after acute infection, especially in certain groups of patients. The article presents a clinical case of a long-term course of new coronavirus infection with predominant lung damage in the form of interstitial changes and persistent inflammation for 7 months from the moment of diagnosis against the background of an immunodeficiency condition due to the patient’s lymphoma in remission after polychemotherapy, exclusion of pulmonary embolism and progression of lymphoproliferative disease. The article highlights the difficulties of determining the criteria for a post-COVID and the features of its treatment using long-term therapy with systemic glucocorticosteroids, inhalation administration of tauractant (Surfactant-BL) in comparison with the dynamic assessment of total ventilation disorders and dynamic control of MSCT of the chest organs. Thus, the importance of identifying risk factors for the progression of COVID-19-associated conditions in patients with different comorbid backgrounds and identifying criteria for the development of new long-COVID treatment strategies is emphasized.