Because primary lymphoma of the appendix is a very rare disorder and commonly presented as acute appendicitis,it is seldom diagnosed by preoperative imaging study. We encountered a patient with pathologically proved primaryappendiceal lymphoma associated with acute and chronic appendicitis. Ultrasonogram revealed a non-compressiblesausage-shaped hypoechoic mass with a linear hyperechoic center caused by mucosa-lumen interface in right lowerquadrant. Post-contrast CT examination showed a markedly enlarged target-like appendix with obliteration of thelumen; the outer layer showed higher attenuation than the central portion. There were also multiple strands in theperiappendiceal fat and thickening of adjacent lateroconal fascia and colonic wall, and this suggested acuteappendicitis associated with appendiceal lymphoma.