Cardiorrespiratory fitness is a capacity to perform, through body adaptations and responses, dynamic activities of moderate to high intensity using large muscle groups, during long time. It determines an important part of possibilities to perform activities of daily living and is closely related with health and quality of life. The measurement of the maximal oxygen uptake (VO2max) as a parameter of this fitness is useful for educating about the physical conditioning and in prescription and control of fitness programs in sick and healthy subjects.The aim of the study was to develop a regression equation to predict VO2max based on non‐exercise data in patients with chronic low back pain (CLBP). All patients (N=70) achieved a maximal graded exercise test with measured VO2max (30.8 ml.kg−1.min−1 +/− 7.7). The regression model included as non‐exercise data, the patient's sex, body mass index (BMI) and intensity of sports activities (IPAS). Multiple linear regression generated the following formula (R2 = 38.3, SEE = 6.08 ml.kg−1.min−1): VO2max (ml.kg−1.min−1) = 35.337 − 0.475 * BMI + 0.155 * IPAS + 7.976 * sex (women = 0 and men =1)The Durbin Watson statistic demonstrated inexistence of problems with serial autocorrelation (D–W = 1.86). The K–S normality test demonstrated that the errors are distributed normally. This study provides a relatively precise non‐exercise regression model to predict VO2max in CLBP patients.