Introduction. Dyspnea, regardless of etiology (pulmonary, neuromuscular or caused by other factors), remains a significant challenge. There is still a lack of effective methods of the treatment of severe dyspnea associated with intensifying anxiety which is the most common indication for intensification of causative and symptomatic treatment or palliative sedation. Case report. A 48 year-old woman diagnosed with relapsed breast cancer with bone, pleural, hepatic and pulmonary metastases with lymphangitis carcinomatosis syndrome confirmed by lung biopsy. In 2011 the patient underwent breast conserving surgery followed by teletherapy, brachytherapy and tamoxifen hormone therapy for 5 years. Comorbidities included chronic obstructive pulmonary disease, diabetes mellitus type 2, depression and nicotine addiction. The patient was urgently admitted to the Department of Oncology and Radiotherapy from Clinical Emergency Department due to rapidly aggravating dyspnea and respiratory failure. Chest X-ray showed massive bilateral pleural effusion and threatening cardiac tamponade. Treatment involved thoracentesis and pericardiocentesis with concurrent symptomatic management. After temporary stabilization of the patient and due to rapid progression of the disease salvage, paclitaxel chemotherapy was started. Despite the features of potential chemosensitivity (chemotherapy-naïve, rapid progression, visceral metastases) the applied treatment was ineffective. After careful evaluation of clinical situation and possible treatment strategies, and after obtaining patient's consent, sedation with midazolam and morphine was applied. Conclusions. This case demonstrated ineffective salvage chemotherapy used in the patient with severe dyspnea induced by a rapid progression of metastatic breast cancer and difficulties in obtaining effective symptomatic treatment.