The invention relates to polypeptide conjugates comprising a polypeptide exhibiting G-CSF activity and having an amino acid sequence that differs from the amino acid sequence of human G-CSF in at least one specified introduced and/or removed amino acid residue comprising an attachment group for a non-polypeptide moiety, and having at least one non-polypeptide moiety attached to an attachment group of the polypeptide. The attachment group may e.g., be a lysine, cysteine, aspartic acid or glutamic acid residue or a glycosylation site, and the non-polypeptide moiety may e.g., be a polymer such as polyethylene glycol or an oligosaccharide. The conjugate has one or more improved properties such as increased biological half-life and reduced side effects.