OBJECTIVE The aim of this study was to define a color space of non-vital teeth and to compare it with the color space of matched vital teeth, recorded in the same patients. METHODS In a group of 218 patients, with the age range from 17 to 70, the middle third of the buccal surface of 359 devitalized teeth was measured using a clinical spectrophotometer (Vita Easyshade Advance). Lightness (L*), chromatic parameters (a*, b*), chroma (C*), hue angle (h) and the closest Vita shade in Classical and 3D Master codifications were recorded. For each patient, the same data were recorded in a vital reference tooth. The measurements were performed by the same operator with the same spectrophotometer, using a standardized protocol for color evaluation. RESULTS The color coordinates of non-vital teeth varied as follows: lightness L*: 52.83-92.93, C*: 8.23-58.90, h: 51.20-101.53, a*: -2.53-24.80, b*: 8.10-53.43. For the reference vital teeth, the ranges of color parameters were: L*: 60.90-97.16, C*: 8.43-39.23, h: 75.30-101.13, a*: -2.36-9.60, b*: 8.36-39.23. The color differences between vital and non-vital teeth depended on tooth group, but not on patient age. CONCLUSIONS Non-vital teeth had a wider color space than vital ones. Non-vital teeth were darker (decreased lightness), more saturated (increased chroma), and with an increased range of the hue interval. An increased tendency towards positive values on the a* and b* axes suggested redder and yellower non-vital teeth compared to vital ones.