To explore the influence of CT findings on the optimal timing of open decorticationin patients with stage III tuberculous empyema. A total of 80 patients with stage III tuberculous empyema who had undergone open decortications were recruited; 44 patients had chest CT findings indicating low-density lines, while 36 patients did not show this imaging finding. Demographic data, perioperative data and preoperative and postoperative chest CT images were collected. In the low-density line group, the duration of disease (P= 0.0030) and the preoperative anti-tuberculosis time (P= 0.0016) were longer than those of the group without low-density lines, and the ESR (P= 0.0218), CRP (P= 0.0027) and leukocyte count (P= 0.0339) were lower in the low-density line group. Additionally, in the median operative time (P= 0.0003), intraoperative blood loss (P< 0.0001), volume of catheter drainage during 48 h after operation (P= 0.0067), chest tube duration (P< 0.0001), and length of hospital stay (P= 0.0154) were significantly lower in the low-density line group than in the group without low-density lines. A total of 88.64% of participants in the low-density line group showed hyperplasia with hyaline degeneration in pathological examination, which was observed only in 41.67% of patients without low-density lines. In addition, gaseous necrosis was considerably higher in patients without a low-density line (P= 0.004), while the low-density line group had a higher rate of treatment success (P< 0.05). Patients with stage III tuberculous empyema presenting with low-density lines around the thickened fibrous pleural rind on preoperative CT imaging may be good candidates for open decortication.