Two major factors contribute to the presence of horizontal forehead "worry" lines--the dynamic (muscle contraction, movement-related) action of the frontalis muscles of the forehead with expression and the static (at-rest) appearance of "etched-in" creases that result from years of daily motion of the frontalis. To treat forehead wrinkles, much like treating the wrinkles of the scowl (frown lines between the eyebrows) and the crow's feet lines around the eyes, you need to address both types of wrinkling. Botox (or Dysport or Xeomin) works to diminish the hyperactivity of the frontalis muscle, which is at the root of the wrinkle formation in that region. However, it takes a filler to smooth out etched-in creases once they have formed within the "fabric" of the skin. In my NY practice, I usually choose Belotero Balance for this purpose, since it possesses little to no tendency to give rise to the unwanted, bluish/gray Tyndall Effect when injected superficially as needs to be done to elevate these lines. (In my Israel satellite facility, where a far greater number of regulatory agency approved fillers are available, I typically opt for Aliaxin FL for this indication). The combination of Botox and filler typically lasts longer than the effects of each alone. One caveat: It is unwise to inject the frontalis muscle lower than one inch or so above the brows as this might result in a brow ptosis. So, for that region, filler alone is typically used. Make sure that you consult with a board certified aesthetic physician and check out his/her before and after photos before agreeing to proceed. Best of luck.