The Chicago Police Department, which has been criticized for failing to follow up leads that could have linked mass murder suspect John W. Gacy Jr. to the disappeasrances of three youths who worked for him, will set up a computerized system to trace missing persons.

"We'll use the computer to look for common denomiators, such as the fact that several missing persons had the same employer," Police Supt. James O'Grady said.

Gacy, who operated a remodeling business, had employed at least three of the youths whose bodies were found buried along with 24 others under and around Gacy's home in Norwood Park Towniship, just north of Chicago.

Only after Gacy was arrested last month through the efforts of police in the Chicago suburb of Des Plaines did any connection between the three disappearances come to light. The three employees were John Butkovich, 17, who was last seen in July Butkovich, 17, who was last seen in July 1975; Gregory Godzik, 17, last seen in December 1976, and John Szyc, 19, last seen in January 1977.

O'Grady denied that Chicago police had been lax in pursuing the cases but conceded that no link was made between the three cases. Gacy, who once served a prison term for sodomy in Iowa, also had been charged with attempted homsexual rape in 1971 and a homosexual rape in 1978.

The police superintendent said the system will begin operating "in the near future." It is expected to cost only a few thousand dollars since existing computers will be used.

In addition to compiling employment information, the system will include data a known associates, personal habits, residence and schools attended by missing persons.

The present system of tracing missing persons relies primarily on exchanging reports received by various divisions of the police department throughout the city. Since more than 20,000 reports of missing persons are filed annually with police, the job of manually comparing similarities in the cases is virtually impossbile under the present system.

O'Grady said when the new system is in effect any policeman will be able to obtain information such as how many persons recently had disappeared in the same area or were otherwise linked.

Gacy, who had told investigators he homosxually raped and murderd 32 boys and young men, is being held in the Cook County jail.