Abstract: An optical symbol scanner assembly has an illumination attachment to facilitate detection and decoding bar code symbols that are printed or formed on mirror-finish surfaces. A hand-held scanner has an array of LEDs or laser diodes on its distal face that produces light to illuminate the symbol. The illumination attachment is mounted on the distal face of the scanner device. At a distal end of the illumination attachment is a diffusion-treated surface such that the illumination leaving the attachment appears as a bar or zone of diffuse light. This is reflected off the bar code, so that the mirror-finish areas appear as the bright or high portions of the symbol and the diffuse areas thereof appear as the dark or low portions. The attachment may be in the form of a block or plate of a clear plastic, or may be formed as a prism.