A plastic bag with a closure tape, including: a bag formed by one or more flexible plastic films attached to one another defining bag walls, a closed bottom, an upper opening which allows accessing the inside of said bag, and an annular fold attached to the bag walls defining a conduit or several consecutive segments of conduit around the mentioned upper opening, the inside of said conduit or of each of said segments of conduit being accessible through at least one aperture provided in said fold; at least one closure tape formed by a flexible plastic film arranged inside the conduit with the ends thereof attached forming a ring around the opening, or inside at least one of the segments of conduit with the ends thereof attached to opposite ends of said segment of conduit; a portion of said closure tape being accessible through said at least one aperture for partially extracting it from inside the conduit or from inside the segment of conduit, causing the closure of the opening; wherein said closure tape is folded in the center along a folding line parallel to the longest edge of the closure tape; characterized in that said closure tape is printed on one of its faces with first messages arranged in a reading direction; said first messages are entirely located in one of the two halves of the closure tape demarcated by the folding line, second messages, identical to the first messages, are printed entirely in the other one of the two halves of the closure tape demarcated by the folding line, arranged in a reversed reading direction with respect to the reading direction; and the walls of the bag and/or of the fold are transparent or translucent, which allows viewing the first messages and/or the second messages of the closure tape through same. a bag formed by one or more flexible plastic films attached to one another defining bag walls, a closed bottom, an upper opening which allows accessing the inside of said bag, and an annular fold attached to the bag walls defining a conduit or several consecutive segments of conduit around the mentioned upper opening, the inside of said conduit or of each of said segments of conduit being accessible through at least one aperture provided in said fold; at least one closure tape formed by a flexible plastic film arranged inside the conduit with the ends thereof attached forming a ring around the opening, or inside at least one of the segments of conduit with the ends thereof attached to opposite ends of said segment of conduit; a portion of said closure tape being accessible through said at least one aperture for partially extracting it from inside the conduit or from inside the segment of conduit, causing the closure of the opening; wherein said closure tape is folded in the center along a folding line parallel to the longest edge of the closure tape; characterized in that said closure tape is printed on one of its faces with first messages arranged in a reading direction; said first messages are entirely located in one of the two halves of the closure tape demarcated by the folding line, second messages, identical to the first messages, are printed entirely in the other one of the two halves of the closure tape demarcated by the folding line, arranged in a reversed reading direction with respect to the reading direction; and the walls of the bag and/or of the fold are transparent or translucent, which allows viewing the first messages and/or the second messages of the closure tape through same.