OPINION OF THE COURT
Memorandum.
The order of the Appellate Division should be reversed, with costs, defendants’ motion to preclude plaintiffs* from litigating the issue of plaintiff Jose Verdugo’s accident-related disability beyond January 24, 2006 granted, and the certified question answered in the negative.
Plaintiff, a food service deliveryman, was injured on December 24, 2003 when a sheet of plywood fell from a building under construction owned by defendant Seven Thirty One Limited Partnership. Plaintiff was compensated for treatment of his head, neck, and back injuries, as well as post-traumatic stress disorder and depression. While receiving workers’ compensation (WC) benefits, plaintiff commenced this personal injury action in Supreme Court in 2004. The following year, in December 2005, while this action was pending, the insurance carrier for plaintiff’s employer moved the Workers’ Compensation Board (WCB) to discontinue plaintiffs benefits on the grounds that he was no longer disabled as a result of the accident. In January 2006, in a WC proceeding, an Administrative Law Judge (ALJ) reviewed the evidence and expert testimony submitted by the plaintiff and the insurance carrier. The ALJ found that Jose Verdugo no longer suffered any disability as of January 24, 2006 and terminated his benefits. Plaintiff appealed, but on February 1, 2007, a full panel of the WCB affirmed the finding that plaintiff’s disability ended on January 24, 2006, and that plaintiff required no further medical treatment thereafter, other than for post-traumatic stress disorder.
In April 2009, the defendants in the instant personal injury *1037action moved to preclude plaintiffs from relitigating the duration of his work-related injury on the grounds that the issue was already fully litigated and decided in the WC administrative proceeding. While the motion was pending in Supreme Court, the plaintiffs’ attorney commenced a separate Mental Hygiene Law article 81 proceeding to appoint a guardian for Jose Verdugo. This proceeding was uncontested and a guardian was appointed.
The doctrine of collateral estoppel is applicable to determinations of quasi-judicial administrative agencies such as the WCB (Brugman v City of New York, 102 AD2d 413, 415 [1st Dept 1984], affd 64 NY2d 1011 [1985]). Collateral estoppel applies if the identical issue sought to be precluded was necessarily decided in an earlier action, at which the party opposing preclusion had a full and fair opportunity to contest the issue [id. at 415-416). Although legal conclusions and conclusions of mixed law and fact are not entitled to preclusive effect, findings of fact that are necessary for an administrative agency to reach are entitled to such effect (see Hinchey v Sellers, 7 NY2d 287, 293 [1959]; Matter of Engel v Calgon Corp., 114 AD2d 108, 110 [3d Dept 1986], affd 69 NY2d 753 [1987]). The issue disputed on this appeal is whether the WCB decided a necessary issue of fact about the duration of Jose Verdugo’s disability and, if so, whether the plaintiffs had a full and fair opportunity to contest the determination (see D’Arata v New York Cent. Mut. Fire Ins. Co., 76 NY2d 659, 664 [1990]).
The determination of the WCB should be given preclusive effect as to the duration of plaintiffs disability, relevant to lost earnings and compensation for medical expenses. The issue of continuing benefits before the administrative agency necessarily turned upon whether Jose Verdugo had an ongoing disability after a certain date, which is a question of fact, as distinguished from a legal conclusion and a conclusion of mixed law and fact.
We also find that plaintiffs had a full and fair opportunity to litigate the issue of ongoing disability in the 2006 WC proceedings. Plaintiff was represented by counsel, submitted medical reports, presented expert testimony, and cross-examined the defendants’ experts regarding the issue of whether or not there was an ongoing disability.
Plaintiffs attempt to use the guardianship order in this appeal to buttress the contention that Jose Verdugo is still disabled and argue that such an order raises an issue of fact as to the duration of his disability. We disagree. The issue of plaintiffs *1038incapacity was not opposed at the guardianship proceeding (in which defendants were not a party) and was based on evidence presented only by plaintiffs.
Plaintiffs are Maria Verdugo and Maria Auqui, who is the guardian of Jose Verdugo.