A process for manufacturing knitwear, hosiery or seamless textile items with variable compression on circular weft knitting machines, comprising the steps of: - providing at least one circular weft knitting machine comprising at least: a bearing structure; a cylinder of the needles rotatably mounted in the bearing structure; a plurality of needles supported by the cylinder and movable parallel to an axis of rotation of the cylinder to produce a knitted fabric; a plurality of stitch adjusting cams operatively active upon said needles and selectively movable to vary the width of the stitches produced by the needles; at least a first feeding device of an elastic yarn operatively active to supply the needles with the elastic yarn at a respective feeding position; a control device of the operation of the knitting machine; and electric and electronic devices connected to the control device and operatively active to control the operation of a plurality of parts of the knitting machine and to detect a plurality of operating parameters of the knitting machine; - activating a program for manufacturing a knitwear or hosiery or a seamless textile item, on the control device of the knitting machine; and - manufacturing a knitwear, hosiery or seamless textile item on the knitting machine; the process being characterized in that it further comprises the step of actively and automatically changing, according to a predefined program for manufacturing the textile item, the feeding tension of the elastic yarn fed to the needles at least by the first feeding device according to a predefined value of variation and for a predefined number of times, corresponding to at least two times within the same knitting row during the production of the textile item, to define in said same knitting row of the textile item a corresponding predefined number of distinct knitting row portions having a mutually differentiated yarn tension corresponding to at least two portions of the same knitting row, wherein - the step of changing the feeding tension of the elastic yarn is performed independently from a variation in the position of the stitch adjusting cams; and - the tension of the elastic yarn, the elasticity and the compression degree obtained in different areas of the textile are varied without changing the knitting structure produced. - providing at least one circular weft knitting machine comprising at least: a bearing structure; a cylinder of the needles rotatably mounted in the bearing structure; a plurality of needles supported by the cylinder and movable parallel to an axis of rotation of the cylinder to produce a knitted fabric; a plurality of stitch adjusting cams operatively active upon said needles and selectively movable to vary the width of the stitches produced by the needles; at least a first feeding device of an elastic yarn operatively active to supply the needles with the elastic yarn at a respective feeding position; a control device of the operation of the knitting machine; and electric and electronic devices connected to the control device and operatively active to control the operation of a plurality of parts of the knitting machine and to detect a plurality of operating parameters of the knitting machine; - activating a program for manufacturing a knitwear or hosiery or a seamless textile item, on the control device of the knitting machine; and - manufacturing a knitwear, hosiery or seamless textile item on the knitting machine; - the step of changing the feeding tension of the elastic yarn is performed independently from a variation in the position of the stitch adjusting cams; and - the tension of the elastic yarn, the elasticity and the compression degree obtained in different areas of the textile are varied without changing the knitting structure produced.