The present invention relates to pullulanase variants having increased thermoactivity and comprising substitutions of the parent pullulanase at one or more positions corresponding to positions 393, 143, 150, 243, 244, 345, 346, 368, 370, 373, 381, 382, 385, 387, 402, 429, 430, 431, 432, 456, 486, 492, 610, 624, 631, 632, 665 and 699 of the polypeptide of SEQ ID NO: 3. The present invention also relates to polynucleotides encoding the variants; nucleic acid constructs, vectors, and host cells comprising the polynucleotides; and methods of using the variants. The variants are mainly derived from pullulanases from Bacillus deramificans, Bacillus acidopullulyticus or hybrid pullulanases.